8 3/4 vs 8 1/4 weight

@Topless69
I’m in the same predicament with a stock 73 340/4 spd. From what I have gathered is that the 8-1/4 is fine for that application. Plenty of gear choices from Doctor Diff and others to support it.
I think if I were wanting to achieve your goals I wouldn’t look at weight as much as I would rolling resistance. I have read that Dana’s use less HP to spin. I would be trying to figure out where the 8-1/4 is in that regard. What s the pinion location compared to an 8-3/4.