In need of windshield replacement on gm 4104 due to vandalism
Jay -Sorry to hear that, it's da**ed maddening, isn't it?
FYI, the front windshields are interchangeable L to R, and the same one fits all the highway GMs from 1953 up until 1980.
Your first call should be to Luke at US Coach in NJ (1-888-262-2434) If he doesn't have them, he'll know where to get them. Also suggest, while you've got him on the phone, that you consider purchasing a new rubber gasket.
As for installation, any competent local glass company that installs windshields on Class A RVs and HD trucks should be able to handle a GM windshield. Make some phone calls to local new RV dealer's service dept, as well as a Freightshaker, Kenworth or Peterblt dealer and ask them who installs windshields for them if they don't do it in-house. Heck, you might even call a local charter bus outfit and ask, too!
FWIW & HTH. . .

RJ