ok. Can you get the same performance out of stock heads as you can out of aftermarket heads? what would the prices be compartiably(sp?)

 

you can port some gt40s out pretty good, add bigger valves but you gonna end up not far off price wise from a set of alum head

 

I have a 289 with gt 40 heads and a 347 with afr heads no way no how even close to the same.
If the gt 40s are a fire cracker the AFR's are a A bomb in comparison.
I looked into the old 351 windsor heads then adding 202 valves like Model65 said your in the price range for some alu. heads anyway

 

You can certainly improve the performance of stock heads, but you would be hard pressed to match the performance of a good set of aftermarket aluminum heads.

 

By the time you modify a set of stock heads to perform as well as some good aftermarket aluminum ones, you're into it for about as much money, but out of room to grow. Most of the decent aftermarket heads are designed with more material and water jackets in different places so that they can be ported a great deal more. Plus aluminum is much lighter.