I installed a 67 1/2 ton rear end in my 48 panel. wasn't to hard. The hardest was the pinion angle.Needs to to be real close, or you go through many a ujoint I was lucky and had the trany end piece to go to the open drive line. Used the drive shaft out of an 62 Chevy 1/2 ton had to have it shortend and balanced.
Good luck.

Been driven and loving my 50 for 27 years. With the same stuff Chevy put in it from the get go.