Here's the thing - Ludwig used a whole bunch of different shell layups without regard to decade or even whether the pieces of a kit matched.
In the early 60's, it wasn't uncommon to find old bare mahogany WFL shells, trans-badge era unfinished maple, and pre-serial-to-'67 white interiors, in any combination imaginable on a kit. '67 is when they started to be a little more standardized, with the clear interior finish, and the edges began to be more sharply cut as they moved into the early 70's. In 1976 (ish) Ludwig began to move away from the reinforcing rings to a thick smooth shell, which are very different drums.
The reason for all this is: If your kits are 1968, and the one you're looking at is 1974, those are pretty similar drums and can be compared apples to apples. But if you've got a mahogany-and-huge-rering trans-badge kit and you're eyeing up a 1978 power-tom beast, those are completely different animals.
So, what you got now, and what you got your eyes on?