Which heads are beter?

[Rev]

With today's pump gas, I think you're better off with 351W heads about 1969 vintage. You won't want more than about 9.5 CR. The 351W heads will breathe better than the 289 heads.
When you get them rebuilt also get them pocket ported and milled some. Make sure the heads you get have 1.85/1.54 valves. In a mild engine, this should be all you'll need. I'd use CC Magnum roller tip rockers for a street type engine. I think you can get all this for about $500. This is the route I took a couple of years ago in my '66 with a 306 CI engine and got 285-300 HP. If you want the exact specs, e-mail me. I have drag strip data too, if you're interested.