rear end swap

[Mel Foye]

Have a 69 Sub 1/2 with stock rear coil spring set up. Want to swap in 8 lug 3/4 or 1 ton--lost my decade old notes on it---which used leafs. Can I switch housing mounts and mount the 8 lug on the stock trailing arms with stock coils?
Reason is, I have converted fronts to 8 lug disc set up and want better brake balance from the bigger rear brakes and it also moves my cruise rpm up because I will go from the 3:07 to the 3:70s which are now in the rear ends.
I have the leafs for the 8 lug but missing one front leaf frame mount so finding that and the playing around that will be needed for ride and height adjustments has me seeking other options. Thanks. Mel