Sounds like challenger 1 found someone who has interest in and experience doing the "older" cars.. The new stuff is way different...

I did Auto Glass from 75-80 when I moved on to outside sales.. I am 62 ( next month) and the guys who taught me are all too old or dead who worked on "our" cars from that era..

If the above guy is still around I would grab him...

PS.. Urethane is used to glue in the W/S to the frame, while butyl is used to seal up the gasket type W/S's...

Urethane "glue ins" replaced the tape kit ( the black licorice seal) used to install glass up to 1974 due to federal laws to help with rollover strength of the auto's roof.... Yes it is a stronger bond and MUCH harder to ever remove the WS if used..

Yes, there are exceptions and I am sure things have changed since I was doing glass, but that was the norm "in the day"..