The belt tensioner/accessory drive is barely off it's minimum adjustment and there is at least 3/4" more adjustment.

I just got off the phone with the machine shop, they can install bronze valve guide inserts the same day as milling the head and they can sonic check the head deck as well to establish a safe number. This is always a chance the head has been milled before too, which would be bad for me!
Rebuilding an OHC Pontiac 250 with EFI and a Turbo