To be honest if I were you I would buy a LM1 or some kind of A/F monitoring device and do it yourself.My smallblock didn't care if the timing was 36 or 38 so I run 36.

If you go into a shop with a dyno and you pay them to set your car up it will cost a bundle.I'm not saying they don't have their place.I've left alot of money at those places and always have done better for my self.

Get a A/F meter