i have a set of 289 heads ported and polished, how much better will they be over stock?
also i have a set of stock 351w heads laying round, should i pp those and throw them on? which is better?

 

unless the 351 heads are from 1969 or 1970 or 351w lightning(gt40 heads) they wont be anything special

 

Agreed. Unless the 351W heads are close-chambered, which they're likely not, you're much better off with the ported 289 heads. They won't flow fantastic compared to an aftermarket head, but they'll be much better than stock. The stock 289/302 exhaust ports are horrible.

 

how about going with a late model head like an e7 etc.

 

an e7 is slightly better than a 289 for flow, but have a larger combustion chamber so your gonna lose compression.


if you want to use something late model look for the gt40 heads 96-97 5.0 explorers are the best place to find them, or 93-95 cobras and 351w lightnings