SteeleRubber Gaskets & Windshields

I don't know why a vinyl top would make a difference in the gasket.
Whenever you do delete or replace the vinyl top the rear glass gasket would need cleaning for reuse or replace. I prefer to clean and reuse OEM gaskets even though removal with out damaging and the cleaning is time consuming.
To pull the rear glass and gasket could very well become vinyl top remove and rust repair. I suggest.. Fall back into the trunk with a flashlight and look for evidence of water leak and rust under the Dutchman panel.
Every job I do snowballs. If I pull the windshield, I'm going to pull the dash too and reseal the vent boxes and wiper pivots, and everything else I can do at the same time. I also did rear glass/gasket R&R, and headliner renew on my 67. I'm glad it wasn't a vinyl top car. No rust repairs needed. Good luck with yours.