I have the opportunity to buy a set of LS6 heads off my friends TA which were originally off of a 2004 GTO. With my current setup (231.237 112 lsa cam, FAST 90, full exhaust etc) would it be worth putting them on as is? about how much power would i pick up?

 

You said originally off an 04 GTO? Is this meaning they were the original heads on that car? Because if so the 04 GTO's had a 241 casting which is not an LS6 head.

If they are 243 castings, yes you stand to gain about 20 rwhp with them.

 

he said they were on a GTO, they are 243 castings though.

 

thats what they were listed as 2 years ago when i bought them. they are 243 heads with the triangle marks near the plugs. they have springs good to .650 on em also. Told ya as they sit good for about 20.......hehe.