Need options for wheels and tires with my free flatbed add on 1981 ford 5 lug

[beoutside]

I came accross a pretty much free flatbed with full kargo master lumber rack so the old rusted bed is now gone. This set up will hold a cord but not safely with those 15 inch rims. Anyone have some thrifty options to upgrade either tires or wheels and tires . Thanks
5 lug on 139.7, low offset I think, bore hole around 100mm on a 1981 ford 4 by 4 heavy half with 3/4 ton new leaf springs. Thanks
I have a quality drill press

 

[dancan]

Haul a half cord at a time or a cord in a trailer that has brakes .

 

[chucker]

swap out the axel for a 3/4 ton and mount 265 16 10 plys for less then what the truck is worth....