Tim, I try to be accurate even to the point of "ad naseaum" because readers use this forum for reference. The picture above with the green engine is a 1954. It has the support, So to me it would be accurate to say 1954 1/2 ton trucks and earlier, with original 3 speed or 4 speed with torque-tube tail housings, have this support.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."