Just to add to what ray and Jason have said, the heads from edelbrock are a pretty much ready to bolt on piece right out the box, I changed the valve job to suit my preferences. The one major area of work is the intake. I had a solid 2 days worth of porting on the intake. Edelbrock did tell me today they intend to build an intake with bigger ports and a 4500 carb flange on it. The one major deficiency I saw in the heads was his, when I cut the spring pockets to accept 1.625" diameter triple valve springs it made pinholes in the top of each exhaust port. I didn't cut the pocket any deeper just cut the O.D. larger to accept the triple spring. I brought this up to edelbrock and it's supposed to get resolved.