Just wondering if there are any differences between the 1.6, 2 and the V6 MK1 capri shells/engine bay?

Cheers, thanks for that! Ok looking at a 2L capri, and I was potentially looking at conversions down the track, to a V6

Triangular plates at the firewall end , radiator mounts not as deep, battery next to radiator support rather than further back, indentation on the inner gaurd next to the battery mount.  Brake lines mount on firewall near id plate rather than just above the transmission tunnel.  No real issues converting to a V6 provided you are not trying to make it look genuine.  Its quite a bit of work to fake a genuine car. Plenty of 4cyl shells with V6 and V8 engines.
 
Hope thats some help?
 
Cheers