A friend of mine built a First Model from scratch but it is different in several ways. He may have sketches.

Packet,
My understanding is that all the actions used to make the Maynard rifles were cast at the same time and were then modified to make the various models. DB may be able to confirm or shed further light on this point.
If the preceding is true, then I may be of some help. I've made a Maynard, model 1873, from bar stock and have the action dimensions, in a variety of formats, mainly dxf files.
I do know that there are some differences between the percussion models and the later models 1873 and 1882, with their riveted on top caps but suspect that the action outline and hole locations, might be the same.
I've found that copying an original example is considerably easier than trying to reinvent the wheel.
Otto

The 1st models were different in several ways but the basic size and shape of the receiver was the same. All the 1873 and 1882 models were made from percussion receivers, some left over from war production and many from repurchased surplus carbines. If chipmaker will share his drawings that is the way to go.

Just using modern steel will not greatly increase the strength of the action. There are other design limitations.

Chipmaker, would it be possible for me to get a copy of your files for the Maynard?
gumpy