Ok. So I think I need some advice on how to proceed here.

Inner and outer rockers need to be replaced.
Both rear cab floor pans need to be replaced.
Both rear cab mounts same.

Best procedure? One side at a time.
1. Remove Rear Floor Pan.
2. R&R Cab Mount Bracket.
then rockers?

I'm not sure how best to go about replacing the rockers and the floor pans and still keep everything all lined up.

 

Well here's the next installment. Left tailgate post repaired. But now all of a sudden the tailgate is rubbing at the top when I close it.Wondering if the post sagged when there was no support at the bottom. Anybody know if the tailgate can be adjusted laterally (left/right)? If not I may be undoing what I did and using something to "spread the posts and re-building. We'll see.

Here's the pics.

 

These posts are very easy to move when some of the structure is removed. Welding did not help and probably pulled the post in. I would see what you can do to push the post back out. Try to use a jack or port-a-power to push it, but try not to push against the other post. You should mount something to the bed floor to push against. You should not need to undo anything you have done, just stretch it back out.

*EDIT* - From the look of your pictures, you need to pull in the passenger side and push out the driver side. You may find it difficult pulling in on the driver side...

 

I'm thinking a come along hooked to the latch might pull the passenger side in. As far as pushing out the driver's side....maybe bolt something into the tailpan as a brace and then a jack? I'll play with it. If I find a nice and easy way to do this I'll let you know.

 

A come-along is a good idea. Just do not pull against the other post.

 

Should I remove the top before doing this or does it matter?

 

I would. You could unbolt the top and prop it up in the back so it is off of the bed rail. That would serve the same purpose.

 

Well I ended using a come along and 115 horsepower "porta-power", (Bulldozer) to pull the left side back out. Just used the dozer as something stationary to attach to, I wouldn't recommend using the hydraulics as just a wee bit too strong. Also placeing some wooden shims between the cable and the post to spread the force of the cable to avoid crimping is important. Pulling in on the right side was the same process.
The, don't know what to call it, lock that slides into the quarter panel near the tail gate locks on the side, had to be adjusted to allow proper alignment of the gate and the quarter panels. All good now.
Off to continue work. More pics later.

 

Good news!!

 

Well here are we again. Floor is back in driver's side. Partial floor on passenger side with spare tire mount.

Got some rockers (inner and outer), floor pans, and patch panels and rear cab mounts today. Could make for a busy weekend.

Got a little sloppy there towards the end. Oh well break out the grinder.

Here's where I'm at so far.