First had to cut metal out welded all the way around. Added extra braces from a 75 bed I had. Made brace spacers from lexan with hole saw. All cross braces leveled front to back. Cut trex type decking to lenth. This had a groove down both sides. Measure width of bed and figured out how much space to put in between. Cut alluminum strips to place in grooves between boards Bed floor is not bolted down it's just laying on braces There is a angle at front and rear over the edge. I'll post pictures but may not be in order. Doing it this way I can take it out and put back without removing bolts.
Are you going to add bed strips? It would be real easy to do, except for all of the drilling in the aluminum. With some careful planning, you could predrill all of the aluminum on a drill press before assembly. I would make the holes larger than the bed strips bolts so that it will be easier to fish the bolts down through the cross sills. BTW, you do not need to worry about having a groove in the bedwood where the bed strips lay like original bedwood. The bed strips work just fine laid on top of your flat boards. I did one of my beds with those kind of deck boards. It looks just like it should.