Where in the Rocky Mountains are you located? I am in Colorado Springs.
I have a low windshield model like yourself (mine is a '67).
I am not sure how you plan to stuff a Small Block V8, RB26 or VG30DETT into the tiny engine bay of a Roadster...I guess anything is possible. To put a clutch on the stock car, requires pulling the engine as the tranny will not come out by itself...these cars are very tightly packaged - which I am sure you know.
I have attended the largest Roadster show in the US, which is in Solvang, CA every year (last weekend in April) and I have seen the Buick 3.5L V8 swapped in a Roadster, if I find a pic I will post it.
The RB is VERY long, and the VG30DETT is VERY wide.
Over on 311s.org there are a few interesting swaps such as:
1) Turbo KA24
2) Turbo Miata
3) A few SR20 Turbo swaps
You should check it out...this is my good friend Mike Spreadbury's most recent work..it is probably one the most beautiful swaps I have seen in any car...350whp in this 1900lb is plain frightening.
As you can see the turbo SR20 is a pretty tight fit itself.
My car is running great on the old pushrod R16 for the moment, so I am going to stay with my stock 96hp. I just serviced the SU carbs this week and continues to run fantastic.
Good luck with your restoration!
Yasin