I will start by saying that Pecatonica is great to deal with, carry quality parts from some of the best suppliers and provide their pre-carved stocks to other vendors as well (Track of the Wolf, Jedidiah Starr to name a couple).
The term Kentucky Long rifle kinda covers "every" rifle built in a number of States (Penn, Maryland, Virginia, Ohio etc) - so it's really "generic".
To put it another way - you have a "Car" (Kentucky Rifle) - your car is a Chevy (made in Maryland). The model is a Chevette (built by John Armstrong) - if you see where I'm going here.
The one (problem - and not really the right word) with trying to make a single stock that encompasses an entire region for an entire period is that you get a mish/mash of a "bunch of builders" and the end product, which stylistically "like" some of the rifles from that period/region, is not really representative of any given builder or an original rifle.
So, if we stick with Pecatonica's offerings, an Early Lancaster might look like the result if you took rifles from four or five builders of the period and stuck them in the blender. Again, what does a "Chevy" look like??? There are a number of models and not one "encompasses" ALL Chevy models.
Their J. Dickert looks "exactly like" a specific early Lancaster rifle.
Track of The Wolf's Issac Haines is also an "early Lancaster" but looks quite different than the Dickert.
The John Armstrong model (Pecatonica or Track), built as a flinter, which represents a "Maryland" rifle in the latter part of your stated period is every bit as much, as the two noted above, a "Kentucky Long Rifle", but looks almost nothing like the Lancaster's.
In the era you are looking at, which is roughly what is called the "Golden Age" (give or take a few years), there were many notable builders making rifles.
So you have many choices in your "era".
While Lancaster's are popular because they shoulder well and are easy to hold for most shooters (compared to many other builders/school styles) it has been my personal experience that absolutely the nicest rifle to hold/shoot is in the style built by J.P. Beck (Lebanon, PA).
If I was building from a precarve, the Beck kit from either Track, or one put together by Knob Mountain would be pretty high on my list if I was looking for a 1780-1800'ish longrifle.
You will get other great suggestions here - my opinion is simply that - my opinion. :grin: