Mortal Kombat 1 has the front of the cabinet that sticks out and that you can slide the PCB out of the front. Mortal Kombat 2, 3 and 4 are all flat fronts. If you have an MK1 cabinet I would restore it to MK1 art and just put whatever PCB you want in it. Below is a link to a custom MK1 overlay that lets you add the Run button for 3 and 4. If you can get MK1, MK2, MK3, UMK3 and MK4 boards you can put a 6 in 1 switcher and have them all.
just something to think about.
www.thisoldgame.com/products/utom-mortal-kombat-cpo