Butyl for new vent window install in new frame

[Chuck Swanson]

I tried cork/butyl glass setting tape on my new vent windows and reproduction frames, but they are too loose as the cork does not bond well on the vent glass.  I'd rather use all black butyl with no cork added, like original as maybe that was used on purpose.  I found on 5/64" on eBay, https://www.ebay.com/itm/CRL-5-64-Sealstrip-Glass-Setting-Tape-Black/331502725023  but only 100 foot roll for $90, and don't need that much.  I checked and the gap is .15 after setting the bare window in frame, so need .075 on each side of glass, and 5/64 (.078) would be closest.   Anyone have a source, or used a specific type to install the vent window in a *new* reproduction frame?  Question is for 65-66, but I think probably the same for many years GM, especially Impalas. 

If someone says the 5/64 has worked for them, great and don't mind buying, but there are so many sizes and I'd have to keep trying vs post here. 

Thanks, Chuck