Heads, how much gain?

Lets start by saying "nothing" is ready right out of the box. That being said if you buy brand new eddy's you will need to have them checked, they are mass produced and sometimes things get done badly. Have a machinist check everything before running them, If you buy rebuilt mopar iron heads go with 906's and I have a guy that sells rebuilt 906's with stainless valves and whatever springs you need for your cam, 5 angle valve job for really good prices, I am running a set of his 360 heads on my 340. Here is the link, his 906's stat at $599 and he has upgrades to your specs. He also sells eddy's for $1399 both assembled heads

http://www.aeroheadracing.com/id6.html