Depending on tire OD,355's might be a bit high.
If you are running a tire that is 24 inch height,that might work w/355's. Also,, you talking being carburated?????
A nice set of 373's would probably work better,but again,depends on what size tire you will use.
Buick GN's have a 200R4 a 342 rear gear,but they are fuel injected & are sequential SP fuel injected (better for emmissions).
I would think running a stock 250 w/an OD trans,you could get 20-25 MPG.
I got 21 MPG w/my 250,Carter 400 AFB ,4 bbl Offy intake,5 speed manual 10-1 compression,510 lift 230 degress duration @ .050 approx(it's been a while)Driving on the freeway to Famoso dragstrip.Bakersfield.
MBHD
