The size is 68" x 74"

 

About all you can do with that size is 2 sheets of 4'x8'...I would use 1/2"...of oriented strand board or plywood ...both weigh about the same...plywood will be more $$. Cut each sheet at 6' and then just overlap the seam and weigh it down with whatever you got. Then just toss it off when you drive the truck..or toss it in the bed.

 

Thanks Spotty.
I bought 2 sheets of OSB. I don't remember the thickness off hand but I know it's not 1/2". Maybe 7/16"? The cutting sounds easy enough. I was thinking that it would not be good to put weight on them. So I was considering running a strap from one side to the other & hooking on to something under the truck. Hmm. Now that I think about it, that would need to be a rather long strap or two. Maybe I should attach eyelets on each end & hook onto them. I did by 2 utility handles to help with handling them.

 

Now you will have to shovel the snow of the plywood so you can remove it.