Tranny and rear end combo question

[bpl0807]

Hey guys, first post here. I have a 1966 Chevy C10 pickup, and in it is a 250 straight 6 paired to a column shifted muncie 318. I absolutely love this truck and wouldn't consider trading or selling it. The truck drives wonderfully for the entire drivetrain being all original, however, this truck is terrible on the highway due to it's gearing. It currently has what I believe to be a 4.11 rear end in it, and at about 62mph im pushing 3k rpm. Recently I have been researching swapping either the muncie 318 for a 319 o/d or the 4.11 rear end for a 3.08. My question being, what do you guys think about either of these swaps, and would the 3.08 gears be ok with the muncie 318 and the 250 straight 6? Thanks, any help is greatly appreciated.