1955 Rear End

[55chopper]

Hey Gang,
Just bought a 1955 chevy Truck. I came with a 350ci/TH250 upgrade. As far as i can tell, the rear end is stock.

My problem is at 55mph i seem to be driving at a very high rpm. I spoke to a rear end specialist and he said i have that is a common upgrade and suggested i have a stock 3:90 gear and should go to a 3:38. But my friend that also has a 1955 truck said its not enough. I should go to a 3:08 gear.

What are your experiances?

thanks