GM chose to bolt-on the rear motor-mount frame cross-member and the rear transmission-mount frame cross-member on 1954/55 1/2 ton Hydra-Matic equipped trucks.

On other 54/55 1/2 ton trucks, the rear motor-mount frame cross-member was riveted on, and there was no rear transmission-mount cross-member on manual transmission equipped trucks.

If movement was not an issue with H-M equipped 54/55 3100s, most likely bolting earlier (47-43) riveted cross members would not cause movement problems?

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.