904: should I switch to 727?

Hi, new to the group!

I picked up a 1975 Dart Sport recently, supposed to have a 360/727, Sure Grip rear. The engine and rear end check out, but the transmission is actually a 904. It is a former hole shot car. I couldn't get under the car when I bought it because it sits REALLY low, and has those horrible ground-dragging headers. Anyway...

I've heard the 904 is better in some respects because of lighter internals, but it's also bad because it has lighter internals that are weaker than its 727 cousin. This will primarily be a street car , but I indefinitely want to be able to put the Sure Grip to use and burn a little rubber. I'm a big kid, sue me. :D

Thoughts? If you say "rebuild it with stronger parts", could you also recommend which parts?

Thanks gals and guys!