Well that's convenient! Lol. Your actually probably not that far off.
After some time with material weight calculators, I've got a couple rough ideas of what I'll end up with.
I was envisioning laying 8" c-channel upright on top of the trucks frame, with 1.5" .120 wall square tubing as frame for the decking.
That's roughly 195lb.
Decking it over with pressure treated 2x12s would add another 240lb, 1/8th" steel would add 180lb, And regular 2x12s would add about 150lbs.
weight now ranges from 345-435.
If I used a smaller c-channel I could knock off roughly 40 pounds, but then I'd have to make spacers so my tires dont scrub at full articulation.