Turfman,
Last night, I debated showing you my table mount, quick change vise's. I built them before Harv educated me. I like his idea best because it is will work any where there is a receiver. My table vise's work great but won't mount anywhere else.
Now tonight you mention working on your tailgate & you ring my bell again. Harv may know a better way on this also, but here is mine, just in case.
16 gauge sheet metal on all of tailgate except where vise slide is, so you have a smooth work table. Be sure to turn up 1/2" at rear so parts don't roll off between bumper & truck.
Mount vise on 1/2" thick steel & make 2 part slide for it to move in. Drill hole to drop pin through if you need to lock it in place. The 2 part slide is mounted in pickup bed and on tail gate. Slide vise in & close tail gate. Open tail gate & slide vise out.
Note: I have 54" parts drawers in my bed which leaves just enough room for my vise.