I am interested in knowing what the rear end gear ratio might be for a 1972 Olds Cutlass that had a 307 cid and a 350 trans. I have this old drive train set up in my 37 Ply and I am getting an average of 16 mpg on the highway. I'd like to get the milage up a bit closer to 20 mpg (highway) and I'm thinking if I change the rear gear ratio it will improve my milage. The 307 is set up with a 650 cfm Edelbrock carb (1405) and sanderson block huggers and 2.5" exhaust w/ two dual chamber Flowmasters.
Thanks.

since your looking to up the mileage, I`d suggest a overdrive transmission, a 700R4 with lockup converter should suit you fine.

That would be great if I had the cash and/or facilities to purchase such a trans and modify my car to carry it. I just finished rebuilding the motor and trans mounts for the th350, I'm not about to make any changes there now. I can handle changing a gear or two in the rear end, but I do not know what my present gear ratio is.

We need more information.

Like: What RPM are you at when you are running 60 mph?

Depending on the setup you have, your mileage might actually go DOWN putting in taller gears.

I guess I'm stuck on this one. I don't have a tach in the car. Oh well, I guess I'll drop this inquiry for the present. I will do a little more learning of the facts about the car and when I have more information I'll bring the question back to the forum. Thanks anyway.