I made a set of ramps out of 2x8s with 2x4s screwed on edge underneath. I cut tapers on the end that touch the ground that match the slope perfectly. I put screws every 6: down the length of the ramps.
I screwed 4 stringers between the left and right ramps. When I use it I take the tailgate off and rest the ramps on the rear bumper. I use a ratchet strap to hold the ramps to the truck. The ratchet strap goes between the top stringer and the bumper. I store the ramps in my shed to prevent rot.
I made this to pick up a basket case 1450 last year. They don't even flex when a tractor is on them.
This is a picture I took when I unloaded my 1450:
