[oldskool]

if your 3 speed is open drive I would put a later rear like an 8in ford with 3:50 3:25 gearing,i had a 46 pu w/4speed open drive,replaced rear with an 70s torino rear and ran 65 mph, just had to mount new spring perches easy peasy,if you can locate a 68-72 bronco rear it will have the same wheel bolt pattern.