Staying true to my username I'm going to have respectfully disagree with the opinions here about the use of white letters on modern day mustangs.
But whatever floats your boat.
IMO, it depends on the font of the letters on the tire and the tire profile. Looks ok either way on Kooldawg's to me. The letters on my own tires do not lend themselves very well to be painted. White letters looked awesome on Goodyear and Firestone tires of many years past.
Heavy's are vinyl he got done at a local shop. I can't think of the name at the moment. You could probably message Emay as I believe he knows. Heavy is on vacation for a while IIRC.