Best Stock BB Heads?

I've never found a single year or model for that casting but I tend to buy engines, not cars. It's a std 906, with an F cast into it. My understanding is they are the most consistently cast 906s made. The SS and FAST guys run them. I think out of 15-20 sets of 906s over the years, I've had 2-3 individual heads that were Fs.
I would ask Dwayne Porter if he knows any specific years to look at. But really, once you go and modify them, any year is fine. The template porting was on the earlier heads and that's where the biggest gains are to be found. That and a very high quality valve job on modern equipment.