Yeah Kurt, like I said looks like the took the low and mid range power of the 2V heads, combined it with the hi revving power of the 4V heads and came up with a really great pair of heads!!! Now, with those bolted on top of a Dart block having 4 bolt mains, then add a 3 piece valley girdle I think you'd end up with a real powerhouse (Trickflow's dyno showed like 540 horse and a bit more torque) as well as good longevity!!!! Oh yeah, did you notice the studs are 7/16" and not the usual 3/8" of the Windsor heads??