Need help o 49 1/2 ton chev

[Oldpatt]

This is my first posting, so bear with me. I have recently bought a 49 Chev 1/2 ton. Back in the late 60's, a 55 chev v-8 engine was installed and mounted to what appears to be the stock 4 spd , closed driveline, transmission. I am considering changing the transmission and rear end to a GM automatic and rear end. What GM rearend comes closest to being the proper width? I would like to change both front and rear bolt pattern to late chev pattern. 4 3/4 I think.
I am also having a tough time backing the brake shoes off enough to remove the brake drums. Does the brake adjusting star wheel turn right or left to back the shoes off? The truck has been setting since 1971, so I suppose it has a right to be contrary.
Thanks for any help or advise you will share.
Oldpatt