Our 14-30P/R dryer plugs are 4-prong and grounding, so I don't forsee any safety concerns that way.
My welder is a 83160 Century wirefeed which is similar to a Millermatic 210... (160A @ 60% duty-cycle, 200A max)
Hopefully if I can standardize a little bit on circuits and plugs I can minimize some of the re-wiring as my shop space evolves.
[This message has been edited by u2slow (edited 09-07-2005).]