CLConard - First off, Welcome to Stovebolt!
A little searching in some Chevy Master Parts Books shows those rear brake shoe return springs for your truck listed as GM# 3694516 (2 each per shoe) for the upper "short shoe" and GM# 3694799 (2 each per shoe) for the lower "long shoe". The overall length of the upper springs are 3-7/16" (green) while the lower spring length is listed as 3-7/8" (black).
I did a quick web search of the GM#s and found none being offered anywhere, but stuff like that does pop up on eBay sometimes. I think your best option is to go ahead and move this over to the
Truck Parts Wanted forum in the Swap Meet and perhaps there is a Bolter that has some serviceable spares or even an NOS stash they would be willing to part with.
Just say the word and I can move this over to that forum and we can see if anyone can help you out.
