I know you can swap barrels for 9mm, but I don’t know why you would, when Tokarev ammo is so damn cheap and plentiful.
I’ve heard reliability might suffer, since the shorter 9mm has to jump forward out of the longer mag, but I have no personal experience.
My Brother was a machinist and a bit of a tinkerer. He actually made his own scope mounts for Mosin Nagant rifles which fit the rear sight base. He showed to to me and it was as solid as could be. The mount extended back over the action so you could use a standard eye relief scope on it.
It looked a bit odd but worked perfectly. His Son and I both suggested he patent it but he thought it was just too much trouble for something which might not sell.
I think the whole idea of using a 9mm barrel with those long mags would be to load the long 147 gr hp bullet out quite a bit leaving enough room for a lot more powder and the space for it to burn. This should feed better and I think one could come close to .357 mag power out of it. The actions are said to be real strong.