Mr. Luver / Luver !
As far as I can tell. The checkered or plain walnut is correct. Re-builds after WWII could have the "corn cobb" type. ( Other's please correct me if I am mistaken ) Just like the model 1200 Winchester that will have various pump wood.
I had a source for "Chinese" heat shields, but it dried up. Now I go to Numrich, and they are about $115 each.
You may have to ream out, or stone the inside diameter to get a perfect fit for the barrel.
If you want a more correct shield, and wish to spend more, go here:
East Taylor LLC, Savannah, Georgia USA
The butt, if it is not cut down in length, use it and mill in the cut away for the swivel, and then inlet it.
Stevens shotguns are the easiest trench conversions to do.
Again, I make these for me, other nuts and re-enactors that do not wish to pay large sums of money, and maybe trash a collectable shotgun.
I do not wish to decieive with the replicas, and will not sell as such! I will always stress this fact!
Mark