What alternator do you guys run with a onboard welder?? Which is the best system...Premier...Mobiweld...other??? I need to replace my alternator anyway so what should I use??

The GM alts are easy to modify into a welder. Basically, they just pull the regulator. There's a writeup on this in the tech section (no, not the BB) here on pirate.

Or search on board welder.