Mark,
You're right, there are several of us who have replace floor and cowl panels on AD trucks, me being one. The pickups and panels are the same from the doors forward, so the same things apply.
As far as sequence, if you also need to replace rockers, that might be your first item to get in place. If they're rusted away at the hinge pillar (very common issue), they are critical to maintaining the door opening dimensions. Other than that, I would start with the floor and toe panels, then work my way out. The floor laps over the rockers, then the kick panels lap over that, then the hinge pillar. That joint is going to be one of the last ones that you should weld. In fact, you'll need to fit EVERYTHING in the lower cowl area before welding anything solid. Use sheet metal screws to hold things in place temporarily.
Take a look thru my pictures. Specifically around
here and working backward in time.
You'll want to brace the cab before cutting the rust out to maintain the correct door openings and hinge pillar location. The Factory Assembly manual has cab dimensions that you should check to be sure things are correct before final welding.
There are others who have shared their experience over in Paint and Body. Some browsing thru that forum might be helpful to you as well.
