these old girls are really simple to deal with.
Believe it or not all of the factory stock brake hard ware is available for them.
There are real nice disk brake brackets available if you want to go that route....
a short tail TH350 will work geed behind the 6.
pull the rear cover and check the gear ratio.
guys have installed both 200R4's and 700R4's in there Earlies.
the drive train out of that 70 pickup would be pretty sweet in that van.
I am running the drive train I had in a 79 Chevy pick up in my early.
Crate 350 factory TH350 trans 3:08 open 12 bolt rear end.

Its a "Van Thing"
A life style you have to LIVE to understand!

Vintage Chevy Van Club