Thanks blokes. The info is going to be very usefull.
Regardless of what engine i run in the little coupe, i will need to run the 1000 rear axle as all the models that were made after it are wider & my wheels & tyres are a perfect fit now. I wish i had known about the 3.7 to 1 ratio before, as i was always looking for another gear once my sedan had gotten into cruise mode on the highway.

It was the ratio problem that propelled me to try the 205/60/13 tyre size. I might have used 195's instead if i hd enough gear. Then again,..... perhaps not.

Thanks again. It looks like i will be looking for a sunny 3rd member in the new year.