Alan, hold down was from Gearhead for like $26...

Pat/John, I'm 99.9% sure it's the small plug - the only two plug sizes that I know of are 5/8" plugs and 13/16" plugs... These are the smaller version, 5/8" - so if I got a diff size they'd be the bigger ones (right? - at this point anything is a possibility)...

@ Tommy - ported spark plug holes FTW! Could I list that as a mod for the car in my sig?!

But all in all guys, seriously, I think it's just best to part with the heads and sell them to someone who is willing to machine them/etc. I've had troubles with everything from valve train lineage, to plug fitment. I think someone else can use them - and I'll roll with a more "off the shelf" type setup...