Sorry! I had to put this project on the back burner. I got engaged and other little things. However, I didn't stop my planning for this build.
Some details - A-PACs will be used since I'll have a modular 270* steering wheel and High/Low shifter on each cabinet side. I will be bad and use 27" 16:9 modern monitors because I do plan on making the computers "budget" powerful so they will be capable of playing modern PC games as well. Sorry if this is sacrilegious.

So I think figured out how to make the left side "hi-jack" the right side to play a single cabinet, two player game, utilizing "two" cabinets. I'm going to use a momentary switch to toggle a USB and HDMI switch; little bit of soldering and warranty voiding, but no big deal. With the push of a button, it should switch the right monitor display to mirror the left display and switch the A-PAC for the right side to the left side computer. Make sense? This operates on the assumption that you can use two A-PACs input to one computer and to my limited knowledge, I think it should work since it is just like plugging in a second controller.
My NEW question pertains to something I wrongfully assumed was incorporated in MAME - LINKED PLAY.
This machine was linked previously and I'd like to be able to have LINK capable games, well link

. Say if I did want to play Final Lap 2 linked play like this cabinet was originally intended to do, is it possible with the two separate PCs I plan on installing? All the threads I've search on for this came up with computer science geniuses who have made it possible on one computer with multiple instances of MAME, but that had its own issues.
Thank you severdhed for your replay.