How 'bout a Turbo from a Mustang or T-Bird. I had a Mustang equiped with one and was lucky enough to rent a 'Bird from Hertz - nice motor and go they like stink and are as reliable as a Timex watch.

Then there are the 4.6, 5.4 and 6.8 Ford modular motors or even the MoPar hemis or truck V10s.

A '76(?) Cad 500 cid or maybe a newer Northstar

Or maybe even a furrin motor like a V8 Toyota or a Porsche 928 V8 tho they have gotten scarce.

The only thing I do have to remind you of and that's leg room especially if you have much engine setback - a problem I'm having at present with seats for my '31 Roadster and that has only a 5.0L Ford tho with a 5" recess