....But there is none of the detailed information concerning screw, pin and thread sizes....
Only a thought, though you likely considered it. Since you're doing all the machining, you can pick the sizes and threading that you want. Maybe, you can base it off of ease of availability and value, rather than unseen historical correctness. An example of this approach is the CPA folks use highwall barrel threading, because it fits their goals better than the original.
Knowing all too well how projects like this can go, I'd think you'd be better off committing to one trigger style and not worrying about converting it. I think there's a distinct appeal for double set triggers, but in use, say fun at the range or out hunting, a decent conventional trigger might be preferable. Again, only thoughts, nothing more.
