the engines in these era of trucks were known as the hi-torque as per GM information.
car version engines were turbo-fire
they had lots of low end torque but low horsepower ratings.
they need the higher RPM to put out said torque, to perform the truck duties.
if yours has a leaf spring rear suspension(G70 on the RPo sticker in the glovebox) then you could fit a 3.31 ratio axle under it if you can find one.... 3.31 ratio started in 1969 and carried over from the old eaton HO52 and HO72 axles to the 14 bolts in 73.
these had the same 42" spring pack distance since '63 or '64. the only difference is the shock mounts changed to staggered in '73..
unlike '72-older where they were both on the same side of the axle tubes,.
3.31 is the least common 3/4 and 1 ton ratio however
3.73 and 4.10 were the most common.
another option would be to go with a 2004r or 700r4 trans, but would be more difficult to convert from the 465 trans, than most others, and certainly more difficult than swapping axles if its leaf type rear