Only use the 351W heads if you can find a good set of 69 or 70 model heads. All the others used the same ports and valves as a 302, or had larger chambers--so you lose compression. These heads work good on a 289--about 25 horse or so more than the 289/302 heads. Check the post by IIBAD4U. I wouldn't bother porting and polishing the smaller heads, by the time your done, you could have just bought the 351W heads, or an after-market head.
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