I'm new to this so if its been covered let me know. Looking to replace rocker, cowl and floor pan on each side of my 55 F100. Just trying to get an idea on which piece to tackle first without having the cab fall apart.

 

Welcome to the site!
If it was me replacing all those panels, the first thing I would do is run some supports across your door pillars and then across the cab from the front door pillars close to the floor before removing the cab from the frame. I would also check to make sure that my doors fit properly, an indication that the cab isn't tweeked, then remove cab to work on it. The rookers could be done with cab on frame depending on the floor panels you are replacing, just nicer to work on the cab removed so you can get at all these with out lifting the cab once its cut up.
I'm no expert at this, (just told you what I did) and those that are will respond with the right way.
Good luck and keep us posted with pics.

 

You can look in my gallery for pictures under body work...the process I took was to first support the cab with braces, then approached the rotten pieces in stages, obviously, you have to get to the floor by removing other pieces, i.e. A pillar, etc...I suggest making a list so you can keep track of what your doing...you don't have to remove the cab, but if your replacing the whole floor you may want to consider that...good luck

 

I did a lot of the same work. I started with the floor because it was my first time doing panel replacement and I figured no one would notice mistakes made there. I then did the rotten parts of my rockers followed by the cowl and rear corners. The one piece of advice I would give you is to take your time.

 

Thanks for the the suggestions. I have the cab off the frame. Do you recommend using the entire patch panel or just the effected area? Next question do I meet the rocker and the floor panel at the bend or do a step/lap joint?

 

as far as using the entire panel, I would replace the infected areas, that way if you need extra sheet metal for something else you have it ( that is unless the panel is stamped), for the step joint, you will have more intergrity by setting the new sheet metal that way for example: I think the rocker had a step joint or flange...but it helps with the panel fitting flush...you can then hole punch the old metal or its nice for a finished product...I have a flanging tool/hole punch that helps out alot...not sure if you can see the picture...

 

I'd recommend replacing only the affected area. I had better luck getting smaller sections to fit perfectly than the larger ones. Depending on what section you're working on, the larger the piece you remove the greater the chance of the cab shifting. Also, a larger panel means more welding and more time. I butt welded all my patch panels. I only had to replace the front and back of my rockers, they were rusted out where the door pillars met them. I have some pictures in my gallery of how I did it.