Does anyone have instructions running a jamma pcb in a cabinet that is the basis of a tv, a computer, and an ipac?
Stop thinking about the computer for one thing. To run a JAMMA board you will have absolutely nothing connected to your PC. You would have to put the internals for a regular JAMMA game in your cab and either use an arcade monitor (which I see you aren't doing) or find a way to convert the JAMMA video signal so that you can use a TV (which I don't know how to do, so I can't help you in that area).
Basically, I think you need to realize a few things.
1) If you are looking for a way to just plug in a Jamma board into some sort of adapter for a PC, it's not going to happen (although that would be cool

)
2) You put Ipac in your last post, I'm assuming thats a typo cuz you mention Jpac a few times, but I just want to make sure that you know the diff and the fact that you need a JPac. (assuming you are going to create a standard JAMMA cab, otherwise you can use an Ipac, but you won't be able to play JAMMA board games then.)
3) You're going to need new hardware to get this running. You're gonna need to a supergun, or a double edge connector, or the internals of a standard JAMMA cab, or some combo of these.
Good luck getting in running. I'm planning to use a Jpac on my cab too and will just plug in JAMMA boards as I get the urge, but my cab is an actual cab, not a hand built one, so you'll have to do a bit of extra work to do what you want. I think its worth it though if you know there are games not in MAME that you want to play.