Crenwelge...unfortunately, i have no idea what series my truck is, the only numbers on my truck are on what i believe is the number plate...

21RD12 5817 does any one know what these numbers mean?

Also, the guy who has the king pins said a rough measurement of the pin is 15/16" x 5-3/32... My frame is in storage currently, this to me seems about what the pins should be... but i cant say for sure..

KC.. are you saying that ur 36gmc has the same axle as the 34 chevy?

I appreciate all the help guys!