Brian, keep your eyes open at the swap meets for the ragged old doors. All of the 68 to 70 B-Body hardtops, convertibles and two door sedan door seals are the same. You can sometimes find a seller who will sell you just the gasket, but I have bought complete doors because they did not want to part them out. A rusty door can yield good parts like the vent window frames, door strikers, door and vent window seals, etc.
For those who are ok with the reproduction door seals, it is hit or miss. All three of the major brands have their distinct issues. The problem is that it is not uniform from brand to brand. Metro seems to have the most pliable material. Soff Seal has the most correct profile. Steele can be good on one production run and the next will have issues.
For the vent window seals, I would try to use the originals. For the convertibles, Metro makes a reproduction. I typically prefer Precision on the vent window seals, but they only make them for the hardtops and sedans for the 68-70 B-Bodies.
Good luck and drop me a call with any other questions.