No, info like you are used to for your Pontiac, something like “PHS Services“ does not exist for your CJ-7. I would think the biggest reason is because AMC was never a well to do company, they were always looking to save money to stay in existence, so keeping track of records fell to the wayside.
As far as hardtops, for the CJ-7 goes the OEM tops have a very specific shape or look, so spottting an aftermarket one would be very easy to see visually. I have never seen in person an aftermarket hardtop on a CJ-7.
The Jeep Wrangler (YJ) that replaced the CJ-7, used the same dimensions for the body, so stuff like the tub, windshield frame, doors and top are the same dimensions and interchange, with a little modification in some cases. For example the YJ tub had a different style tail gate, so the hardtops were slightly different, despite the fact the dimensions are identical.
Having said that, a YJ hardtop can be made to fit a CJ-7. The YJ hardtop is easy to spot because the side windows are larger, among other features.
I have never used a seal on either CJ-7’s I have owned. One was a new model that I bought off the dealers lot, and I don’t remember there being any seals. The YJ‘s did use some form of seals, and they can be used on the CJ-7 hardtop, but I wouldn’t mess with it.
Your CJ-7 is more likely to leak from the cowl seal, where the windshield folds down, than from the mate between the hardtop and the windshield frame. Mine has never leaked where the hardtop and windshield frame attach, the overlapping design is such that it deters leakage.
Post some pictures of your hardtop and it will be easy to see if it is OEM, or aftermarket visually.