Both sets of heads or the motors ? I assume the motors by the comment. Ifso that stinks & is always a rude awakining !
I just took them my heads & told them exactlly what I wanted. How much I want them milled so I know what my combustion chambers will come out at , & told them exactly how I wanted my springs set up ect.. I always do everything myself with the exception of any machine work. That way I know that it is done right & I know exactly what is going on. Not that there arn't great reputable engine builders out there that do what they say they & will do no more no less , because there are many. the guy I took my heads to is an old friend of mine from my street racing days & I have much confidence in him.
That is the key , Having a good working relationship with a machine shop that you trust. Almost like keeping a good banker or 2 that is willing to work with you. It seems atleast for me in this sport that they are both very important.