Coalman,
All the ideas above a great, but each different because each guy needed something different.
I am different still in that I desired all my then owned welders and plasma on one roll around cart....So this is how I fingered out the power problem....I found a ripped out really nice metal box contractors had tossed in trash at work...It was perfect size to contain 3 each 6-50R's....Sucks, in about two hours that sucker was installed on the cart I was building to hold my Mig, Stick and plasma.
That was two years ago...NOW the cart holds different equipment(upgraded), but I STILL love that 3 outlet gang box!
I installed top quality swivel lock casters on cart and hangers to hold 50' of 6-3 extension cord....I simply unwrap however much extension cord I need from cart and plug it into my only 6-50r in whole shop...I leave all welders and plasma plugged in to gang box on cart....50' of cord allows me to roll cart anywhere in my shop.
I have plenty of 240V outlets in shop, but only that one 6-50r type is required.
You might decide to place the plasma on same cart as welder, so consider my idea.