Ahhh.....where to begin.
This is the Davis vs L&R lock. This why they use the L&R for their kit. The Davis is too high for a 1" breech.
The upper reveal of the lock panel is determined by use of the proper breech and is cast into the standing breech. Many people think this small line is a casting flaw and file it off before they start building the gun. Fatal mistake.
The L&R drip bar has to be used with the L&R lock because it has a long bolster and won't work with the Davis bar. However, it has to be located after the lock is inlet and ends up like this.
In doing so, one must be aware of the depth of the nipple hole because you can't just lay the bar on the barrel and solder it flush with the bottom of the snail bolster. Metal may have to be removed from the bottom of the snail to adjust the lock. Results can vary with a dangerous condition occurring if too much is removed.
You can also see that the lock is not a good match with the standing breech at their intersection. In this case, the lockplate has to be fitted to the standing breech. This causes to lock to be moved forward slightly and can change where the trigger hits the lock's sear bar. There are many other little details to pay attention to and I see no way a proper gun can be built with all the components pre-inlet.
To further add complications, the breech/tang combo is cast off center with one side being thicker than the other. If you just face them off smooth, this is what you will end up with. These castings are not fitted, you must do it yourself.
There are numerous small details which have to be worked out in advance or they will bite you in the butt.