MKb.42 to the MP43/44

The MKb.42(H)had it's gas-tube above the barrel,extending forward almost to the muzzle.
The MKb.42(W)had a more pronounced straightline design with the back sight on a tall block.
Both rifles used the curved magizine box ahead of the trigger/pistol-grip group.
The MP43/44 lacked the extended gas tube;instead, a ball-tipped rod projected from the gas-port assembly.
If you want to be historically correct, you can tweak it.
Take your MP43/44,cut off the barrel and the ball-tipped rod that projects from the gas-port assembly.
A. Insert two small brass rods similar to the barrel that has been removed one above each other. The barrel on top will represent the extended gas-port, which it will extend forward almost to the muzzle.
B. The barrel will be just long enough where you can put the sight.
The MKb.42(H)rifle butt closely resembles the MP43/44.
You will be amazed how closely both of these rifles look resemble each other.
If it was me, I would try it,just to see how it comes out. If all else fails, use the MP40 and it's ammo pouch.
Is your project going to be entered in a contest?
Can make for a great conversation if anyone asks'about the rifle!!!
I hope this helps.

Henry