8 3/4” is a lot stronger design and easier to work on. The 8 1/4” with a suregrip I think is rated for up to 350 Hp. So would be good with a healthy 340, the info is on Dr. Diff’s websight. I’d use the 8 3/4” rear end if you can. Stock 4 speed would of been 3:55 gears but you could go into the 3:90s and still be good on street with a half built up 340. Just use the backing plates and all the brake parts from the 8 1/4” on your 8 3/4” then you can use the stock 1973 duster parts, a lot easier to get. Order new axles and sell the small bolt ones on here. There is a guy looking for a set he just posted in the wanted forum. Use money towards the ones you want. I think I sold one of my extra sets of small bolt axles on here for $100 and $35 shipping.
