I use two 5,000 Lb, rated straps with D rings on each end over the rear end axle tubes held by two 5000 Lb. rated ratchet strap hold downs on the rear end hook to two d rings in the floor and two of the same straps and hold downs looped around the K member in the front hook to the front D rings by the front ratchet tie downs
Works good, last a long time.
If I'm towing more than 50 miles, I will stop once and retighten the rears They will stretch a little and get a tiny bit loose