Track's "kits" were actually a parts showcase in their catalog. Meaning they showed the reader how you could put their parts together to make whatever they showed in its finished form, sometimes with variations in hardware. So if their "kit" was close to some gun that was envisioned, or an actual gun that the buyer wanted copied, the example was right there in color, and any changes were easier to decide upon for the buyer/builder. So the kit section was a kind of static informercial, so to speak. Instead of the Rifle Shoppe where you might get a single, full length photo of the piece, then a parts list, Track would give you several images, and you could see the part as well.
Further, you could get some services done, such as having them cut you dovetails for sights and barrel lugs, and breeching the barrel.
So as the others have written a lot of the vast array of parts and especially locks and barrels has dried up. So no use showcasing completed gun with images from 6 years ago, when only the hardware and the lock are in stock and the correct barrel is out-of-stock and Colerain or Rice are not planning on a run of that barrel anytime soon.
LD