Well, on the "works good" I can recommend the Branda Shelby ones, a very soft trapezoidal one. I used it on my Cal Special and it did fine. But as this is the concourse forum did not think that would be what you were after...
I can dig up the specifics if you want.
Please do, if you do not mind.
Looking at that photo, I'm pretty sure Charles' car doesn't have an OE trunk gasket on it. Maybe it is Concours, maybe not, I'm not a Judge. But going by the photo & his original comment and some of the same I have bought, eaten, returned and on and on... I can judge that there really is some garbage parts being passed off as "Concours".
Everything has it's tolerances, even at the Concours level. For example, looking again at Charles' original post. He, like the rest of us seem to, wants a recommendation of a good reproduction trunk gasket for a 67/8 mustang coupe/conv., as well as everywhere else for that matter, on our cars. I think we need weatherstrips or "gaskets" for these cars that do a tadd better than what we see & hear all the time about these cars. Having to return NEW parts that just plain don't FIT the application it is designed to fit on, isn't quite the same as returning a part that "doesn't quite look the same" as an O.E part. Acceptable replacements are what we are all seeking. If these replacements meet or exceed the quality of 1967, 1968 or whatever, in looks and fitment, even better! Technology has evolved at warp speed, quality went down the toilet.
Give it another 50 years or so and see how these old original rubber parts look then, chances are unless these cars are encapsulated in a perfect environment, virtually NONE would be usable at all. You might think at least ONE parts manufacturer could actually attempt duplicating original parts a bit closer than what we find on popular restoration projects as these cars are.
Richard