And I think that's the key, is getting an engineer on board early.
Another person posted a link to skid factory, who have just put an old Cummins in a fairly new patrol, and when I asked about it, the reply I got was it only needs to meet emissions. But these fellas, 1. Know what they're doing and, 2. have mates in just about every department, from tuning, to fab work, to ecu programming, which also seems to help a lot. I mean, hell, they've also been putting a 1500hp Barra into a Bedford, which the owner wants to use as a daily.
What you mentioned in your post about modified cars being registered doesn't seem to mention the era motor the emissions had to comply with....Really, that is what this thread is about...Can the op get an earlier model engine legally engineered into a later model car?