who to buy rhs heads from

They are a VERY good head for the money.

Don't worry about the flow. If you are putting a 500 lift cam in, .600 flow numbers mean nothing and are insignificant.

The RHS's that Brian at IMM does work better, flow more and have better components than the OOTB ede's that still need to be checked for valve job, guides. Less money too IIRC. Ede's have more potential after you port the snot out of them and want a 550-600hp mill. Sounds like that's not what you want.

Send him a PM (member OU812) or call, he can help you out.