See my post
here....
IMO, for most applications, the early W heads, properly prepped, even in uported condition (except for smog knorbs being removed) can give the best bang for the buck spent, especially if you have access to low or no cost machine work for the valve job. The ones I used on the race car were essentially free, other than the cost of the parts (think I had about 300.00 in good valves, rocker studs, guide plates, guides, seals, springs, keepers and retainers...but that was in the early 80's *G*).
Personally, given today's gas, I think they'd be fine on a 289 (and even better, a 302 *G*) if one was running flat-top pistons, not dished....
Aftermarket heads definitely are better in stock form but I guess it depends on how fast you want to go and how much money you have...*G*
Have fun!