Different size tranny mount bolts for different year A-bodys?

Hello friends. Just a quick unimportant question...I've noticed the transmission crossmember bolts on my 1970 Dart take a 9/16" socket (3/8" bolt) and on my 1968 Barracuda, the trans crossmember bolts are much bigger which take a 3/4" socket. (1/2"bolt) Is this normal? Did chrysler change bolt sizes over the years? The holes on my crossmember dont look to be drilled like some hackjob would do it, looks factory...







These are "A-body trans crossmember" bolts from R/T Specialtys and they are the same size for like a 70 Dart...not a 1/2" bolt.



I'm simply just curious...:)