Alvin,
If you want a quick, sure, and strong seal, the modern sealant route is probably the better method.
If you want to go the original route, original-style tape is still available and the removal/installation techniques are described in Shop Manuals (they worked for me). The main problems that people have when using original tape (using the original installation technique) is that glass thicknesses vary and tape thicknesses vary. No knowledgeable vendor will assure you that their tape will work with your glass - they might be able to sell you the correct tape if you buy the glass from them (but even this route has failed me).
Restoration Specialties, Inc. sells glass setting tape in the original composition (and in a more modern composition) in a variety of thicknesses.
After buying and using a variety of thicknesses of tapes, and using them on side windows, vent windows, and Suburban rear-side windows, I have only had one loose fit - on a vent window. A vent window glass has to have a very tight fit because the frame gets pulled down when you tighten the "spring-loaded tension" nut at the bottom of the vent-pane-frame (inside the door).
Tim
