[jumpsoffrock]

These trans are geared for low speed acceleration hauling loads and are not really reliant on increasing low end power or torque. They're reliant on being low geared, which they are.
More favorable ratios of car trans like Muncie m21 close ratio can really benefit from an extra 50 ft/lbs torque because they are taller geared.

I don't think I'm smart enough to teach you what I'm trying to say, but the point is a truck trans like the 465--part of it's designed purpose was to MAKE UP for low power engines using lower ratio'd gears--so you could get work done no matter what engine ya got.


This diminishes the value of increased power/torque.(mainly because you have to change gear before gathering an ideal amount of speed).
Yes, you can help stave of this "issue" by changing your rear end gear. But The most ideal thing you could do is also changing your gear ratios--and you do that by swapping to a different trans.
You sound like you have a simple need for this truck, I think you'll be perfectly happy with your current drivetrain, as long as your rear ratio is numerically lower than 3.55:1.