The year model and body style can make a huge difference in what fits the best. No one manufacturer makes a complete kit to cover an entire car. Some of the manufacturers even buy from each other to have product coverage.
We have been manufacturing and providing weatherstripping for over 28 years for these old cars. It is hard to beat the factory door, roof rail seals, door end cap and U-jamb seals. Some items will wear out after all of the years and will need to be replaced. The most expensive is not necessary the best solution and the cheapest is almost always the worst solution. I would also not suggest using the generic types of profile seals. Purchase the seals with the molded corners and such.
Knowing that it is a 68 Cuda Fastback, Precision makes a quality front and rear gasket for the glass. Metro makes a decent pair of door seals. Roof rail is a gamble from any of the manufacturers. I like the Soff Seal quarter glass seals and Top Catwhiskers will be your best bet for the window felts. Several different variations on the trunk seal, just depends on how correct you want it to be. Expect to pay from $550 to $900, depending upon the manufacturer and vendors that you choose.