Thanks for sharing with us, Herb.
Building from a pre-shaped and pre-inlet stock can be frustrating, especially when it's a parts set that has been around as long as Track's Jim Bridger Hawken kit.
The history of the kit may explain some of the issues you have identified.
Back in 1975, Ron Long designed and started producing the original breech and tang that GRRW used with their Bridger Commemorative Hawken rifles they built for The Montana Historical Society as well as their standard late Hawken pattern rifle they made post-1976.
Ron sold his lock and breech plug business to Tim Houseweart at the end of 1981.
Houseweart continued to make locks and breech plugs using Ron Long's patterns for a few years then decided to sell the business again. Tom Faux bought the flintlock pattern and R.E. Davis purchased the other lock patterns and the breech plug patterns. R.E. Davis produced the Ron Long designed breech & tang for a decade or two until they had some problems machining and drilling the nipple hole and flash channel which they couldn't overcome. They ended up selling or transferring the breech plug business to Track of the Wolf.
Since the days that GRRW used the breech & tang from Long's original castings, the molds have passed through at least three other owners. The original molds probably wore out years ago and new molds had to be made. It's not surprising that one would see differences in the castings that Ron Long made in the late 1970's and the castings that Track is producing today.
You are correct in stating that Doc White traded GRRW's original master Hawken stock pattern to Track. You are also correct in stating that Track made some changes to the pattern.
GRRW's master pattern was shaped but not pre-inlet. The GRRW gun stockers hand inlet all the parts on their Hawken rifles.
Track first listed their Jim Bridger Hawken kit in their Catalog #11, copyrighted in 1986. In their Catalog #14, copyrighted in 1997, Track describes the Jim Bridger stock as, "Precision pre-inlet and shaped on Allen's five axis pantograph. Green River Rifle Works made the master pattern. Michael Hayes refined and perfected our working pattern." Basically, Michael Hayes made them a new master pattern with inlets. They've probably had to make additional modifications since such as the entry pipe.
GRRW's contract with MHS for the Bridger Commemorative Hawken prevented them from selling any Bridger Hawken rifles or using the Jim Bridger name in any advertising. They had to make small changes to their late pattern Hawken rifles so they weren't the same as the Bridger Commemorative Hawken rifles. Some of the changes were that they did not file a square corner on the inside of the butt plate where the crescent meets the heel extension. The forearm on their standard pattern Hawken was a different length than the Bridger Hawken. The barrel lengths were generally different. The location of the barrel wedges weren't necessarily the same.
Track was not a party to the contract between GRRW and MHS, so they can sell a Bridger Hawken. But it it mostly marketing. They probably tried to make their kit similar to some GRRW Hawken rifles, but they didn't try to duplicate the original Bridger Hawken.
Track's Jim Bridger Hawken kit will make a good copy of a GRRW Hawken rifle, but not an exact copy of the original Bridger Hawken.
If you were to attempt another Bridger Hawken copy, I would recommend starting with one of Tiger Hunt's pre-shaped Hawken stocks. They have the barrel channel cut and the ramrod hole drilled, but no inlets. They leave plenty of wood so you can shape the stock to match a particular pattern. The photos below show a GRRW Hawken rifle at the top, a Tiger Hunt Hawken stock, and one of Track's Jim Bridger Hawken stocks next to a life size photograph of an original Hawken rifle.