200-4r budget build


Overdrive lover
What is a must do for a 200-4r in order to have a good while with it if my engine is a 78 chevy lm1 and I have some 3:73's in the rear although my axles are 7.5's.
I came acroos it like thank with a 350 trans but the 350 sounds like its dragging and it burns gas on the hwy.