I got the castings off the free heads The E6's are from a late 80s Mustang have heart shaped chambers, I read in a article that E6's are better then E7's at high torque/low RPM which one of these would be a better choice for a truck would these be a bolt on to my 302 or would it need some heavy machining and not be worth it? I really don't know what the heads are on this truck, this 302 was Frankensteined with a 84 302 and parts from the original 79. the block is from the 84 used the crank out of the 79 as for the heads no idea.. I don't any thing about heads.. Any help you could toss my way would be awesome guys thanks so much.