OK, lets look at some '70 model GTO's. The 1st one that comes to mind belongs to Todd Kuhn. It has the 455HO with #64 D-port heads. The 455HO round port heads were not available 'til the '71 models. Todd has run his car for several years now. Right now, it's the only '70 GTO I know of that is still in Stock competition. If ya'll know of others, please post info, & pics if you have 'em.
I remember a '70 named Kathy's Clown. I have a pic of it running against Rock Running's Super Sleeper.
The '70 Judge that Knafel Pontiac campaigned, ran mostly in AHRA competition. I'm not familiar with their rules. Looks like maybe you could run a different 4-barrel carb, and maybe even a 2-barrel ??? Don't think these were considered Super Stock classes. Pic of the car seem to show small tires. Maybe some of ya'll who know can explain those old AHRA rules.
This article says the car won a couple of nat events, set multiple records, & won the championship in 1970.
https://www.mecum.com/lots/SC0509-79...iac-gto-judge/