Re: Onboard Power Welder install
Do you mean one that runs from an alternator? I imagine you'd have to either isolate your van's electrical system, or add a second alternator that could be isolated. Guys often use a big truck 24v alternator, one with an external regulator so you can get around it. Finding somewhere to put it can obviously be a problem. Seems like a lot of effort unless you're using it frequently, but if you need a second alternator anyway it could be worth it. Check over at jeepforums.com.
I've seen guys use ReadyWelders; they're constant voltage so you just hook it to batteries, usually a few if you need to weld anything even slightly thick. There's an instructable out there that shows how a guy bought a used spool gun off eBay and hooks it to batteries to accomplish the same thing.
Of course people weld with sticks off just about anything. You might even be able to find some sort of control board out there so you could try to regulate the current and/or voltage, or you're stuck with output that might make for only emergency welds.
2001 Ford E250 Sportsmobile with Salem-Kroger 4x4 conversion