If you live in Hungary...
Getting hold of a 6 speed ZF from a more modern BMW M3 should be of no concern for you
Keep the bellhousing from the "Autodramatic" and splice it with the ZF.
If you can weld yourself, making a equal length header is really not a too big hassle on a 960 or 7/900 platform, alot of space
The trick is placing the turbo UNDER the header between the engine and fender (which is not a problem, you'll need new stronger and more rigid engine mounts anyway, it'll make a ton of torque), and the pipes really just need to be within 10-15% lengt on a turbo system. If you do just small changes to the cylinderhead a GT35 would do for 500+whp on 98 RON
Even with stock RN type head with the older NA cams should provide 400 whp at 1 Bar boost (2 bar absolute).
My main concern about theese engines are the cylinder cracking problem, but if no more than 500ish whp, small aluminium bolt-pieces between the liners and jacket will make for the needed stability for long lasting durability.
I would also fit the earlier type NA cams in it, since the cam pullies are adjustable (the slots kan be made longer in a mill if necessary) and set the LCA angle to 115-116 deg. The stock compression on the later T6'es (of RN type) is something in the region of 8.8:1 so setting the cams straight up or even +3 deg. advance with that LCA angle should provide for a quite boost tolerant setup
If you are going to run stock inlet valves I'd fill some epoxy in the ports, thay are a bit overkill in size for the stock valves. I'd fill epoxy in the floor halfway down the port to shrink the MCSA a bit, and add a small amount to the "roof" just before the seat
I happen to have cut one of theese heads in two so i could post a pro paint-edit on a picture of a cut-through stock N-series head (quite similar to the RN in the critical "needs epoxy" area) Somehow Volvo screwed up (as usual) the last portion of the port...