Frame is much different Bill. 9/64" vs. 3/16" thickness and
taller by close to 1/8". Although the front looks the same,
the 3600 frame is very narrow in the back compared to the 3100.
http://chevy.oldcarmanualproject.com/chevyresto/5070.htm Also the cross members are quite a bit different with the 3600
using a center support bearing in it's drive shaft
and no support at the rear of the transmission.
DG
