another reason the 322 may have been used as there may have been a surplus of 322s as there was a fire I think at buick in 64. they may have also hooked up hydramatics behind the 322 as the fire affected the dynaflow section.
322/hydramatic would have been the eng-a/t setup for a GMC I gather with an a/t option. that would have been the same hydramatic used from 54-62 behind the buick. 6 cyl or poctiac eng
that trans was used in olds and caddies from 54-56 and some buicks
ron
ron

http://s908.beta.photobucket.com/user/padresag/library/turned%20works
http://s908.beta.photobucket.com/user/padresag/library/furniture
and a little history of where I come from
http://forum.woodenboat.com/showthread.php?156542-old-boatshop-in-Steveston