OK, Andyel I'm sure it is who can tell you exactly the crack with an unmolested AAZ, and understand your sentiments on that. But they do go OK with the JX gear, but one does wonder about the fuelling and boost matchup... it can't be quite as accurate as the straight AAZ.
Make sure you get the 4 bolts that hold the turbo to the manifold on the JX out in good condition, or find 4 good 2nd hand ones. They cost £13 each! Although you can get socket cap-heads Grade 12.9 to match cheaply, which will do the job... mine had the two longer ones like that in it originally but they both broke when removing, required power-bar undo them all. Re-tighten on re-assembly to about 35 lb-ft with copper-slip on threads but not under heads. Those mating faces have to be very flat and clean - I used a sheet of 80 grade emery on sheet of thick plate glass to do the turbo after de-scaling it, and I stuck same stuff to a perfectly flat thick brass plate to do the manifold (in situ) - using spray-tack adhesive - worked just fine - will find out if I've succeeded this weekend.
Do check the turbo you end up with for play in bearings and condition of compressor blades - info in our Wiki on that. Waste of time puttinga a worn turbo on, in fact if gland-seals bad and you overfill sump, can wreck engine (allegedly, mine just about survived). Make sure you have the proper air-filter for these engines too, and it's clean, they do not like sucking against a restriction (turbo gland-seals again).
Maybe talk to Andyel or Andy Simpson before you finally decide - think it will depend on your facilities and fabrication skills for exhaust and engine mounting... it IS worth it though, if you've found a good lump, they are incredibly strong and quite powerful enough.
And make sure you get a full set of the sump setscrews and bolts form the JX donor, don't tighten the ones from the bellhousing until all the sump set-screws are at least nipped up, and a couple at the back (front carwise) near the bellhosuing might require a 1/4" drive socket set with the right bit and long extension, think i bought a nice Halfords 1/4" set in a wee black box for that. Mine had the windage tray and built-in rubber gasket on it, but most discard that and use a normal sump gasket - your guess, your choice
