Steel base farm trailer, how to build on ?

[chainsaw_louie]

I have this old but strong and functional steel farm trailer base. 

Can someone please explain the expected construction design for building up the wooden trailer bed. 

The welded on vertical tabs are supposed to connect to wood framing members but exactly how isn't clear.  Should two heavy 4x10" rails run from axle beam to axle beam with 2' overhang ?

And how about attaching to those steel uprights ... should the wood beams go on the inside or outside and bolt up tight to them ?

Or should a beam run side to side and slide down into those brackets then front to back beams sit on top and support the floorboards ?

Confused. There is an intended system to attach a wood platform but I can't see it .

Thanks !

[beenthere]

The running gear supports the wood flat bed (or a gravity box). Bolt the front to the axle, but just loosely chain the rear axle, or visa versa.

[chainsaw_louie]

Wow, nice and thorough video all about hay wagons .  Thanks !

[JD Guy]

The running gear supports the wood flat bed (or a gravity box). Bolt the front to the axle, but just loosely chain the rear axle, or visa versa.

Really appreciate this! I have a JD 963 that needs a complete deck rebuild and this answers a number of questions that I had!
Thanks it was very timely and helpful