Boy Alan I have a big ole heavy vice that would work well on your first piece you bought ( pipe with plates on both ends) might have to make the base a little larger. I have to make a weld cart also, I was going to revamp my cart I use for my plasma torch for the torch and the 255 but once I started reading in the 255 manual it said that the 255 needed about 18" on each side for cooling so this axed that so its back to the drawing board.
Mark
Garage stuff
Everlast 255 EXT
Miller 251 mig
30A spool gun
Miller 211 mig
Lincoln SP 250 mig
Lincoln buzz box
Thermal Dynamics
Pakmaster 75XL plasma