Highway mileage is all about air resistance and gearing. I have an 83 123 bodied car running a euro 617 NA but with a 307 diff and a manual five speed OD tranny. I get 35 running 75 mpg with it.

My body is getting shaggy now and I am daydreaming about a 190 body with the same drivetrain. I would then run a 265 diff and I bet I would get 45 mpg with no trouble.

The larger motor would be offset by taller gearing.

Of course you could get better mileage with a 2.2 motor, the 265 diff and a stick od tranny but I am not sure the little 2.2 would pull that tall a gear.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.