The Stovebolt Site Forums The Shop Area Making a Stovebolt Bed Done with the cab; ready to start the bed: questions begin!

I'm guessing you could adapt this bed mounting to your frame. If you're lucky the suspected mounting points that I circled in red match up with your frame dimensions (see attached pic with markups.) It looks like the holes at the rear have a weld nut with threads in them from your first picture for bolting from the bottom. Measure the frame mounting holes and see how they compare with the bed. You'll need some blocks (or some welded in pads) for the bolt locations to reinforce the bolting locations if they aren't thru one of the cross-sills. The forward holes will be closer together (side to side) than the rear ones.
It's just going to take some measuring and maybe drilling some new holes either in the frame or the bed floor.

[on edit] The centermost cross sill may interfere with the frame hump over the axle. But that can be moved or modified if necessary.

Good luck