Re: 351 heads fit on 289?
If you can find an older set of heads from a 351 windsor the chamber size is smaller. These start with a C = 60's and D = 70's. example C9 =69, D0 = 70 Etc. 351W heads also have the benefit of larger valve sizes 1.84" int vs. 1.78" on the 289, and 1.54" exh. vs 1.46" on the 289. Only problem with the older heads is they don't have the hardened valve seats like modern heads do. So running unleaded gas is kinda hard on them. You can have the seats cut out and hardened ones installed, but that gets into a bit of money.
Unless you're going for the OEM look you're much better off starting with a set of GT-40 heads, these have the same valve sizes as the 351 W heads do. Not the GT-40P's though,(which came factory fitted on Ford Exploder's) those have a funky spark plug location and require GT-40P specific headers, which may not be available for your particular ride.
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