So I'm debating whether to go with 35's or 37's. Now I know that this isn't a bronco but I wanted to get the attention of some off road guys (planning on posting this on pirate4x4 later tonight.) Any way 35's or 37's price is out of the picture because both sizes I'm looking at cost the same. The truck is a 1961 f250 with a 302 making about 325 hp and 350 ft lbs through a 2.96:1 case 5.72 granny and 4.56 in the axles. would 37's be too much, make it a dog? It tears up the 33's that are on it. Also what all your opinions on the best way to lift it with out a kit while maintaining highway performance?
TIA

 

Welcome!
I would first use a ratio calculator like this one. Gear Ratio Calculator You can put your current setup on the left and then change the tire size and gear ratios to find the engine RPM range that you want to run.
I'll let someone with more experience with that generation of truck to assist with the lift questions.