[sclor]

Millspec:
Couple of thoughts:
If you have front drums riveted, they are likely original to the truck. Surprised at how long they have lasted. I had to change one of my fronts. I found grinding the head off of the river to be the easiest way to take it apart. I believe the Chevy drums for the front will be the same as your front drums.

Rear drums are a different story. We have Dana 44 rear vs Chevy that use "corporate" rear. Our rear drums do have more offset than Chevy. When I had this problem, I found the front drums for 4 wheel drive Chevy ilate sixties used six lugs and Dana 44 in their fronts. Those drums had fins but were the closest I found for use in our rear. You can use search function and find my posts in the past on this or I can look up the part on Rock Auto if you want me to.

Hope that helps..
Regards
Steve
New Orleans