Hey, welcome to the board.

I have some info...

MK final was 5.0 (there is also a 9.0 prototype)
MKII final was 3.1
MK3 final was 2.1, but was upgraded into:
UMK3, witch final rev. was 1.2
and MK4's final was 3.0 as you stated.

I have NO idea of where to get these, maybe ebay can get you some.

There may be more than this list, but these are the most well-known ones.

MK1:
Prototype 9.0
1.0
2.0
3.0
4.0 (I think this was the first version with Reptile)
4.0 T-Unit (new hardware Midway started using at this time)
5.0 T-Unit

MK2:
L1.4 (There may have been a prototype version before this, but it's not well known if it exists)
L2.1 (Baby basher version)
L3.1 (This is the last U.S. revision)
L3.2 (This is the European version)
L4.2 (hack)
L9.1 (hack)
Challenger (hack that lets you fight Smoke, Jade, Tsung, and Kintaro in the normal battle plan before the ?)

MK3
1.1
2.0 (has free play glitch)
2.1

UMK3
1.1 (has free play glitch)
1.2

MK4
1
2
3 (has added fatalities)

MkI revision 3.0 was the first revision with Reptile. Just to let you know. I would try ebay.com that's the best place to look for PCB boards. I'm trying to get all the mk Pcb boards to except Mk4. Mk4 sucked

Was MK1 prototype 9 before the first arcade MK1 or after revision 5?

The prototype was the first one. Boon made that one and then made some changes for the next one (1.0), because the prototype Gore was real hard to beat. So the revision 1.0 was the first one to come to the arcades the prototype never did.