It's been about 7 years since I installed the windshield on my '41, but if I recall correctly, the seal I got from Narragansett in the 80's was continuous but has a seam on the bottom side and centered on the glass. I would install it on the glass and join the ends with 3M super weatherstrip adhesive while taping it firmly in place while it sets. It is probably form-fitted to go on that way and should be of the proper length.
The glass installs from the inside. Be sure to use the proper kind of sealant. I made a 2x4 prop to hold the glass in place while I installed the trim, which is what secures it.
If you have the dashboard out for woodgraining, be sure to install it first because the windshield trim must be removed to install the dash.