Well, nuts!

Mazda Miata is still 6" too wide.
Really do not want to get into a complex modification scheme. 

Any suggestions for an IRS at or near 50" track?

Got a chjance to identify may Jag rears.
All are Salisbury!

Posi unit center is 60-63 XKE, first model type.
Also an earlier XJ6 open diff that is much more complete but still missing brake calipers, cage,and some other small parts.
The complet unit I just got from an XJS turns out to have an open diff, not the posi it should have been. 
At least it was complete despite having a bad pinion bearing.
In theory I can put the gears or center from the early unit into the late cradle and axles.

I would put in a high winding small block with an IR 4 Weber intake, T56 trans, shave as much weight as possible, and replace those brake rotors ASAP.

Those brake rotors are frightening, over-drilled AND chromed.
Weakened and hydrogen embrittlement, not a good combination.

Just picked up a complete XJS rear at the local Pick N Pull for $170.00
This one came with 2.88 gears and a bad pinion bearing.
No loss as 2.88 is junk to me.
So long as it will bolt up to my other diff's it's fine.
Have to figure out what type each is so I can decide which to rebuild first and get the right brake set-up.

Off to pick up a Triumph GT-6 in the morning.
It had a turbo Buick of some sort in it and the rear has already been converted to ???? IRS instead of the original.
Big ugly hole in the bonnet will have to be cleaned up.
Getting it pretty cheap so breaking my vow to stop buying more projects.
It gets a hot-rod 225 Buick V6 and Saginaw trans, Muncie or maybe a T5 WC if I can find one cheap enough.

MUST STOP BUYING PROJECT CARS NOW!

Strange, only a short time ago they were pushing for E15.

I'm still looking for corn-suger free fuel but it appears the only way to get it in this state is to buy AVGas or racing fuel.

Gues he's not so concerned with pleasing Iowa since he's on his second term.

Old Spitfire uprights are a bit notorious for failing at the lower trunion.
Very small four bolt PCD.

My current plan for it is a hopped up 225" Buick V6 and four speed.

I also have a similar issue with my Marcos 1600 GT as it also uses Spitfire front suspension.
It will have an Alfa-Romeo 2000 engine.
I need to change it so that the hubs can match the Alfa rear axle.

I've finally found out which Cortina parts to get, even found the uprights in Aluminum!
Still working on the new A-arm's

Cadillac 8-6-4 was far worse than the Vega mechanically.
I doubt a single one ever lived to the end of the warranty period.
None ever ran long enoug for rust to be an issue.

Only the GM diesels built on gas engine blocks may have been as bad as the 8-6-4.

Had a Pinto for a while, actually a fairly good car for what it was, cheap drive it to death and throw it away machine.

Well that was a surprise.

Had not realized that the Jag rear uses heavier wheel studs.
Have to buy different lug-nuts to put the wheels on for mock-up.

Did you ever figure this out?

I'm putting a Jag XJ6 rear into a 1968 El Camino.
Also looking into vented rotors, and have CNC equipment of I have to make my own parts.

Still cannot edit my prior post.

Here are a couple of pics of what I got.
No brakes, so I probably have to visit a local Pick n Pull for cores.

I did get two diffs, one 3.54 and posi.
Glad to find it is MUCH cleaner inside than out.

All bearings/pivots have to be rebuilt and the LCA's probably reinforced.
Glad that I can avoid having to shorten anything.
I did confirm that my 8.5" wide wheels clear the hub carriers with room to spare.

So I'm going to be looking at what can reasonably be done for the best mounting and lower trailing arms arrangement.
Not sure about the need for a watts link.

Main use is improved handling over the GM 10" live axle.
Hoping to use one coil over and one air shock per side.
The El Camino is lighter than an XJ6

Unless the other guy back out I have a good trade going.
My tired SB Chevy 400 for his 3.54 and posi XJ6 rear. 

Once in a while CL works.
I will be anxious until the deal is done this coming Thursday.

Okay, "Edit" still not working for me so here's a late update.

After much web searching I find that the XJ6 rear is stated to be 61.75" wheel flange to wheel flange.
The original El Camino rear is 62.50".
The Jag is 3/4" (.75") narrower.
Divide by 2 to get the difference per side, 3/8" (.325").

So an XJ6 or XJ12 rear should be about perfect and no modification to width is needed.

As I measured an original XJ6 wheel the back rim edge to the mounting face is 4.8"
The mag wheels I want to use are 3.5" but are also 8.5" wide.
I have trial fit them on the car and they fit with plenty of space to the inside, and adequate clearance on the outside.
Gaining 3/8" on the outside will make them about perfect!
If I've done the math right my new track will be 63.9" at the center of the tire.
The original rear track was 59" using skinny little 14" rims and tires.

It's possible I might even be able to get away with 10" wide rear wheels (295/50-15 tires!), if I could find a set with the correct back-space.
Probably will not go to the 10" wide rims, would look great but tire selection and speed rating get pretty poor.
This is to be a fast road car, not a dragster.
 

Okay, got pics of the rear of the "New" 68-72 El Camino frame this morning.

Original is a live axle with unequal length trailing arms and coil springs.
Looks to me like the spring perches will have to go, so much for a bolt in conversion.
Also seems all the 'Vette rears I find are Dana 36 from automatics, or overpriced.
If I really want a Dana-44 'Vette rear it looks like I would have to buy a whole car this winter, then sell what I do not need.
Looking even more likely to be a Jag set up.
Just need to determine which to use, XJ6 or 420.

Also intend to fully weld all seams and add some cross bracing for added stiffness.

Some pics to show what I'm working with.
 

As seen from the front with the rims I want to use.
Tires will be replaced with the same size in a modern equivalent, 265/60-15.




3/4 angle from the front.




Close up of the cross member and spring pocket from the front.
The bracket to the front on the main rail can be removed with IRS.




Looking forward from the rear.




A low angle looking from the rear.
Might remove some brackets and box this in if I can.




That spring pocket sits right at the top of the frame arch.

A Jag 420 rear should be about exactly right.
Around 54" as I recall.
Much harder to find than XJ6 but more likely to have a posi in it and lower ratios.

A 420G rear is the same as an XJ6, it's a much larger car than the 420.

May have made some progress of sorts today.

Went looking for a '68-'72 "A Body" frame or rear half to use for mocking it all up.

Found a good one in a wrecking yard, $700.00.
I don't think so!

A "Slightly damaged in the front" at $400.00 on CL.
Better, not a winner.

"Wrecked in front but the rear is fine, $200.00"
Hmm, maybe.

I only need the portion over the axle and it can be from any "A" body of the correct years.
With patience I should be able to find a damaged or partial one just about free.

I already have a spare rear sheetmetal clip.
Once I have the spare frame section I can get serious about working out the fabrication.

Also found an overpriced C3 'Vette rear which the seller cannot even describe properly.
Cannot say which center section it has, ratio, or if it is a posi unit.
Pretty sad from a "Professional".