Thought I'd take a moment to share a recent experience which could have been much more expensive than necessary.
I took my Jag Rear to my favorite mechanic.  He said he's done several rear rebuilds and this shouldn't be too bad.
He researches a good rebuild kit from Randy's Ring and Pinion and gets a Yukon rebuild kit. 
He does the tear down and starts the rebuild process. Like a good rear end rebuilder, he keeps the old bearings and enlarges them so they slip on and off easier.
So far, so good.

Four days of labor later, he decides he is in over his head.  He can't get a good mesh pattern between the ring and pinion.  Too high, too low, too left, too right.  He's managed to hit every wrong combination possible.

At this point, he gives me a call, tells me how many hours it's been and he can't get it right.  He asks if it is ok to send the work out.  I ask who and he says Mark Williams.  I say sure.  A week later Mark Williams is done and they only want $300 for the rebuild.  BTW, these can be very persnickety to rebuild, nothing is as easy to rebuild as a Ford 9 inch!

My mechanic, waved the four days of labor he invested in the rebuild!  Which I think a good reputable mechanic should do since they didn't complete the job they signed up for.

The point I want to make is, before going to a general mechanic, see if you can find a specialist.  Even if you have a mechanic you like, ask what they will do if they run into problems.  Had my mechanic not been such a nice guy, he could have charged me for 32 hours of labor @ $90/hour! 

Assuming we couldn't come to an agreement and went to court over this, he likely would have won because there wasn't an agreement or a limit on his labor.  My mechanic may build good race engines and be very knowledgeable in certain areas, but a Jag rear isn't one of his strengths.

BTW, I recommend the JAG rebuild kit from Yukon for one reason, it has sleeves for the carrier so you don't have to drill and tap a ring gear from 3/8th to 7/16th!  Might have to put them in a freezer to get them to fit, but that's much easier than drilling and tapping a ring gear.

If you don't know the company Mark Williams, I recommend checking them out:
http://www.markwilliams.com/
They are known for race and custom axle setups.  At one point (by their memory), they supplied the hardened chro-moly 30 spline axle stubs to CWI.  They also do custom CV joints etc.  Odds are they already have a blue print or a CNC program for anything needed on a Jag rear.