Thanks to all & for all the ideas. MusicMan70, I esp. like your 'burb setup--cool recess in that tank to allow the nice chain fall adaptation. Too bad I lucked up on a plain alum. cell at the salvage yard for $20: it is symmetrical w/o a recess
My truck is (was) finished, later model steel bed grafted in and rhino'd, but now looks like I'm gonna have to modify a tad & install an 'inverted wheel tub' in one corner for hauling a spare--thanks, 62 Longbed, for the idea & pic. Prolly gonna use one of those space-savers from the '80's in the process.