So after going to a race this weekend I am thinking about jumping up a class next season, but I am going to need some more motor. I have enough parts lying around to make a cheap 468 but I have no heads. Now weight is not an issue so I was considering either dart iron eagles or world merlin 3 cast heads. set up for .750 roller these heads are only 1600 a pair. how big of intake runner should I be considering, they make these anywhere from 269 to 345. has anyone had any experience with either of these heads.