You can check all the truck parts vendors. I think for sure the rears are probably not available new. Some of the vendors offer used drums. If you measure your drums you may find you can use them.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!