If you are referring to the tack strip that is along the outer perimeter of the door . . .

. . . simply cut new 1/2 inch strips of waterproof panel board to replace the worn tack strip.
Two thicknesses of panel board is almost 1/4 inch. Five thicknesses will measure 1/2 inch.
If the metal tabs that hold the tack strip in place are broken off, pop rivet the tack strip in place with 1/8 inch aluminum pop rivets.

Yes sir Fred for some reason I could not think of "tack strip" , sad. That sounds simple enough! Thanks for your help Fred!

The panel board is a good idea. Especially if you have a bunch of scraps of it laying around.
I have always used the convertible tacking strip. Weather its for tops, headliners, or any number of other things. The 5/8" X 1/8" stuff is too wide for some headliner applications such as rear or side windows in many cars. So I just made a simple rather crude jig to cut it down.

https://www.classicindustries.com/product/153039.html

https://www.ebay.com/itm/55-56-57-Chevy-Above-Windshield-Tack-Strip-NEW-1955-1956-1957-Chevrolet/311004754002?epid=1188096574&hash=item486953f052:g:qooAAOSwFL9TuAbk&vxp=mtr

Hey Andy, I like the jig. Great way to trim the plastic tacking strip. I used to belt sand the edge off until seeing your method. Thanks

The supply company had that tack strip so went with it. Thanks for the advise!

When I use cardboard for tack strip, I apply a layer of two part epoxy over top smoothing it out with a piece of foam. I find that it not only gives strength to the cardboard it also holds the staples better.