So where is the best place to start now that I’ve gutted the truck?
Was thinking of starting with the rear floor since I’m new to welding this might be the easiest place to learn as I go and there is a great write up on how to take it out and replace.

What else should I be looking for and are there any metal pieces on the frame that I would want to replace as I go also?

Are there any cross sections or supports across frame?

The last picture is the rocker box which are both rotted out so looking for a rollbar to add in to help stabilize the flex since they are not replaceable from want I’ve learnt

 

Good luck! I'm in a very similar boat with my '74 going off of what I can see. I haven't put a lot of time into tearing mine apart yet nor have I done a lot of searching for repair panels. From what I can remember though, the '73-'75 full verts aren't as supported in the aftermarket as the later years.

The front floor pans (under the seats) are different and I have not found the correct ones anywhere. I think this is a problem for anyone with a '73 thru '77-ish (whenever they moved the front of the bed floor back to give a footwell to the rear seat occupants).

Most of the rear bed floor stuff is available as patch panels that must be stitched together. I think someone makes a complete floor for the later models, but as with the front floor expanding rearward in the later years, the rear bed floor shortens up as a result so those bed floors would not fit in our trucks directly.

I have somewhat resigned myself to the understanding that a lot of what I need to replace will have to be formed by hand.