There have been some inquiries about doing OBA. In additon to what else has already been listed in the tech section regarding OBA, here are some other links. Some of these might be duplications.

http://www.tmcom.com/~tsm1/scout/faq/77onboardair.html

http://www.4x4wire.com/tech/portable_oba/

http://www.jedi.com/obiwan/jeep/york_tank.html

http://www.ajeepthing.com/on-board-air.html

http://www.offroaders.com/info/tech-...nboard-air.htm

http://www.jeepsonly.com/How_Tos/On_Board_Air/

http://www.jeepaholics.com/tech/OBA2/

http://www.4x4led.com/tj/oba/index.htm

http://www.fjcruiserforums.com/forum...ir-system.html

http://www.coloradok5.com/york.shtml

http://www.visi.com/~bsimon/jeep/my_air.html

http://www.jeepaholics.com/tech/OBA/oba.htm

http://www.ford-trucks.com/article/i...Board_Air.html

http://www.izook.com/tech/samurai/body/oba/oba.htm

http://www.toyotaoffroad.com/Article..._Board_Air.htm

http://www.jeeptech.com/body/york/

http://www.planet4x4.net/forums/fzj80oba.php

http://www.geocities.com/Baja/Dunes/...ssor_tech.html

http://www.ericsxj.com/oba.htm

There are a lot of Jeep OBAs designed around either a York or Saginaw AC pump listed here. These are not based on a Power Tank or ultimate Air set up, but rather around revamping the AC pump. Aside from the fact that you have to use on in line oiler for the Toyota AC compressor, all the rest of the information works with any AC pump. Saginaws and Yorks being the cheapest and most readily available due to the fact that most American manufacturers used them in everything-trucks and cars.

Here are some links for a portable system:

http://www.4x4wire.com/tech/portable_oba/

http://www.fjcruiserforums.com/forum...ir-tank-2.html

Josh the next one applies to your regulator question:

http://bargainkeep.com/inventory/kitchen.php

This is from Josh and is a source for some nice cheap regulators:

http://www.extremegearoffroad.com/st...me.php?cat=451

I hope all this information helps. As you can see there is an absolute ton of information out there on it, for tanks, and also using either an existing or a piggy back (as in the case of Toyota..BudBuilt.com used to make a piggyback York bracket for a Yota) York or Saginaw AC unit. I would read what is there, make note, especially on any troubleshooting issues, and build it up. Remember that someone has done it, sorted out the problems and also written about it...somewhere. You don't have to reinvent the wheel....