I got this idea on the forum here, but wanted to share a pic of my bed lift setup. I put short 2"x2" pieces under the bed rails for the 2x4's to rest against. After I got the 4x4 perfectly centered, I added clamps to hold the 4x4 to the 2x4 on each side. Probably not necessary, but I was really paranoid about dropping the bed, especially since I moved it across my driveway to another spot in the shop.
I recommend lifting the bed just a little at first, and watch whether the front and rear bed mounts are coming up at the same time, so you don't get it too far in the air before you realize it isn't centered. I took the tailgate and bumper off, and my 4x4 was 35" back from the inside front of the bed. The 2x4 under the 4x4 was just there to rest the 4x4 on while I got everything hooked up.
