[Adger Smith]

That NHRA Legal AFR head was a special limited production run by AFR that was done a few years ago.
They may be back in production now. I haven't checked lately.
I think the only way you can get them now is find a set someone has stuck on the shelf or quit using. When my old friend RJ Sledge was running the SBF 289's and 302's I know he had a couple sets of iron and a set of the AFR's.
MR. Rock Professor has "Failed". He has failed to look at the NHRA specs for different Fords. Mercury and Ford have some different specs for different bodies and year models. Ray hit the nail on the head when he said you have to research the NHRA specs to see what is allowed. He has one of those Gems.