Tailgate Alignment

[ssjody]

My truck came with the tailgate missing so I bought a new aftermarket tailgate from from LMC. Got the gate painted, bought all the hardware I needed and mounted it on the bed but couldn't get even close on aligning the tailgate to close and be flush. In fact I found that the Bed is actually racked a little. I took a measurement from the front and rear stake holes and found that my measurement was about 1/2 in more from left rear to right front. Uggg...
I guess when the previous owner had the bed reworked that maybe they didn't have a tailgate or it was an afterthought.
My question is this. Can I loosen everything up on the bed (bedsides floor etc.) and get this bed squared up or is it a bigger issue than that. It almost seems to me that if I could pull the left side forward to square it up that my tailgate would then lay flush on the right side.
I'm definitely not a body guy so if you guys have ever ran in to this and have any suggestions on how to solve this problem I'm all ears.