I dyed myself (rit dye) on the stove in very warm, but not boiling water - believe me, boiling water warped and therefore ruined the plastic on several of my belts. Rit works great. Just keep rinsing until the dye no longer bleeds off. I was told to soak the belts in a water/vinegar solution as the final step, this will prevent the belts from bleeding. Good luck!
70 Mach 1 (351C 4V 4-speed) I've been restoring since '96. 95% complete. Also have a '68 HT (289 2-speed) that I restored between '97-98 and is FOR SALE! The VMF has proven to be an invaluable resource for information, humor and excellent advice.