OOMOO 30 is the silicone compound I got off of ebay to make the molds.Two parts mix 50/50. There is also a spray on mold release agent, which I highly suspect is silicone lube spray in a $9 can. It takes some force to remove it from the port. I found that by sticking a large Sharpie 3/4 of the way down the middle of the intake gasket side to create a void,the rubber could "collapse" partially and ease removal.
The Edelbrock heads maxed out at 305 c.f.m. at .500" and stayed flat after that. They have a 2.200 valve with a 30 deg. seat. The goal was to maximize low and mid flow. Pushrod pinch has been opened and they got a general smoothing and straightening treatment. O.O.T.B. flow numbers were in the high 280's,right about the same as Edelbrocks advertised numbers.