From what I've been able to figgure, Audi's NF, NG, 3B and 7A engines are all 2.3 litre. Do they use the same block and are the internals different from N/A and Turbo variants? Also, could you bolt a 7A head to a NF/NG block?

Reason I ask is that there are more than a few NF/NGs out in the local junk yards, but ideally I'd like to have a 20v DOHC turbo engine, which seem hard to come by.

Thanks!