you can use a 76 new Yorker rotor/bearings/caliper on a 83 truck as it is still the small wheel bolt circle.

cant say on the spindle?

if it had 10" drums in rear you can up those to 11"x2.5" and a HD 12"x3"

or disc brakes for the rear.

I have no issues in my 88 440 truck with stock manual brakes 11x2.5 rear drums.