#302 or #308 heads?

I agree with the "run the 308s" people.
They are worth whatever someone gives you for them. IMO a few hundred which I'm sure is far less than what's in them - but that's the market. There are better heads available for a little more money so unless you find ignorance you won't get top $$. As far as gettign the 308s done to what I'd consider "right", anywhere from $700-$1200 depending on the shop labor and the parts used.