Looking at the TM 9-2320-289-34P Parts manual, Figure 150, the bushings for the rear springs are listed as #13(front) and #5(rear)
#13 - GM 350544
#5 - GM 468481
If you look at the diagram and the part numbers, the listing has a UOC numbers. This is the "Usable On Code". On page #4 of the parts manual lists what the "usable On Code" means. The M1010 is truck code 210.
Your parts house should be able to cross reference the GM part number.
NAPA is showing the following numbers.
GM 350544 - NCP 2741189 - $19.69 ea
GM 468481 - NCP 2741785 - $14.49 ea
You will need two of each.
It took me awhile to read your question. as we usually don't use TEXT Message words on this site.