Well, I don't have an onboard air setup currently but I'm planning on putting one in. I've got a couple parts for it I scored cheap but haven't really set in stone where everything is going to go.
For the compressor I've got a brand new
Extreme Outback 24v milsurp unit I picked up for about $100 and for the air tank I've got a 10 gallon tank that, I believe, is a HEMTT air tank according to the part number which I got for $30. The tank is a little on the large side so I'm having a little trouble deciding where I'm going to put it. Can't put it under the bed because most of that space will be taken up with a rear winch. Thought it might fit up under a rear fender but I'm pretty sure when the suspension is under decent compression it would hit it. So at this point I'm thinking on top of the driver's side fender (I've got jerry cans mounted on the passenger's side). Supposedly the compressor is rated for continuous duty use by itself but I wanted a tank for possible limited tool use. Don't really need to worry about an impact driver though since I've got a Roboimpact 24v. I probably should have gone smaller on the tank but for the price I couldn't pass it up. If I can't make it work may have to look at a smaller one but I hope not. 10 gallons of air is a nice reserve.
Haven't decided where the compressor is going to go just yet either. It's decently sized though so it will need a little room and I want it above where I might submerge it. The nice thing is the Extreme Outback compressor can be oriented however I need it for mounting.
Going to plumb in a front and rear quick disconnect to hook up hoses and tools.
I figured 24v because, why not! I've got 200A of 24v power available plus the compressor was super cheap for what it was!
I'll start tackling all the specifics when the weather warms up.