1972 c20 father son project ( help with the rear end plz )

[shotgunjim]

we found our truck in an estate sale in central Illinois . the owners son told me after we bought it that it had never been in the snow or left out in the rain and his grand dad hardly ever left the farm with it . its hard to believe she was about 95% rust free , I know central Illinois right !! we put a fresh paint job on her after we did a complete tear down and rebuilt her inside and out.the experience my son and I had was priceless but now we want to do the rear gear it has the eaton ho52 10 bolt coil spring rear end I think its a 456 gear . we want to put a 355 ish in it . this is 2 wheel drive 8 ft bed. smb 350 , Muncie 4 spd. any ideas ???? plz