Just wondering, if I could actually find a Kalart in good condition, is it possible to easily replace the one for the other? As in, are the mounting holes the same? Or would I need to have new ones drilled?

William

Piece of cake!
You'll need a new coupling arm and you will have to drill a few holes for the mounting screws. Or not, as they're wood screws. I just spotted the screws with a pointed punch and drove 'em home.
Just make sure the shaft for the arm is centered in the hole in the side of the body and the top and sides of the Kalart are square to the edges of the body.
Top

With any luck, you will find a nice Kalart complete with the arm. Just check to be sure the arm is the right one for the camera you are working on. 2X3, 3X4 and 4X5 are all different. I'm not sure, but there's a small chance that your arm will work.