Mechalicallythe ABZ should fit, but i do not know, if there is a chance to fit the PT Distributers in the ABZ heads.
AFAIK the ABZ has for each Zylinder a singel Ignitioncoil.

Maybee yo cann look out for a AEC Engine from the C4 S6,
this one wil fit with only changing 2 temp. sensors. AFAIK

I dont know who did it but sombebody swaped a complete drivetrain with engine from a S8 into teh V8

Gude Mario Audi 100 CD Autom. Bj.83 Audi 200 20v Bj.89 Audi 5000 Bj.85 Audi V8 3,6 Autom. Bj.88