You got it cornbush, you are looking at a highly modified type 38 Jap action, there is now way that anyone now days would even consider doing such a job.
As far as safety, as much crud that was in the barrel and action its been shot a bunch. I checked the hardness checked and also did a Magna-Flux, it shows no cracks of sub-surface indications. As far as it being a cast action, it don't take much to tell the difference, mainly because cast would of had to be welded with Nickel rod and it would not blue. And the day I cant tell the difference between a cast and a steel action will be the day I close the door on my shop.
Being a gun smith and a welder from what I see it wont bother me at all to shoot the thing. It must have concerned the builder somewhat he added a 3rd recoil lug. Even the trigger is a modified type 38 trigger it is adjustable for both pull and creep.
My hats off to who ever did this, I only wish I knew who it was.
A friend will help you hide, a real friend will help you hide the body's.