the frame is round (ideal to flip/rotate). For the frnt bend 2 straps around a sim sz pipe till lapped over itself. Drill 2 holes, press onto frnt legs, bolt thru both @ the 2 wheelhouse edges semi-permanant (till it breaks frm wear) 3 if ya want. On the back - do not bolt dwn. Make a plate & (is it a) 'turn buckle' (or is it a 'thumb latch'?) looks a lill like the winged nut to hold a spare tire to the bulkhead or tail gait. At any rate 1 of those swiveling fasteners that U can turn round it's center bolt. Bolt that to the floor & twist over the back legs. Lock w/a screw hook if needed (a lock 4 inside of a screen door).
Not fancy but gets er done. 'S Y I got a bronk after all (not a mall crawl).