We have been selling and making weatherstripping for these cars for 28 plus years. Personally, to get the best fit and function, you will need to mix and match from different manufactures. Year and model makes a huge difference. The 1973 model year was a transition period and the applications do differ. For door seals, I would strongly suggest using the originals. All of the reproductions will end up tearing up near the A-Pillar. We sell just the clips as they can be easily replaced. For U-Jamb and door end cap seals, either Steele or Metro will work. Again personally, I had rather use good used ones. You may end up having to grind some of the rubber away from any of the reproductions as they tend to be bit too "fat". Typically, the Steele roof rail seals will be better than the Metro piece. For vent window seals, depending upon application, Precision Gaskets I feel fit better. For the quarter pop out windows, Precision is the only manufacture of this piece.
Just because you are thinking that you are buying a piece from one manufacture does not mean that it is their product. These businesses will purchase from other manufactures and rebag so as to have product coverage. As a manufacture in this area, production runs can vary. That is why you can talk to one person and they will swear by Metro, a second will only want to use Metro and third will prefer Soft Seal.
Many vendors will only stock one brand due to the cost associated with carrying multiple brands, but it is our opinion that to provide the best for our customers, that you need to offer a more diverse product line which covers multiple manufactures. It requires more work possibly from the customer, but you will be happier with your purchase. Also being a smart shopper can like wise find just as good prices as purchasing through one vendor.​