Question 1 how far do I need to grind away all my old undercoating which still seems functional but pretty ugly.
Question 2 is my new front floor patch panel bends suppose to fold over my existing bends? even the rails? how about where the new pan meets the firewall..is my new bend suppose to slide between? and finally..my new pan is being held back from fitting snug by my cab corner gusset plate..does my new pan need to be notched out? Here are some pics which may help. My last pic is the outside bottom of my cab..yikes..a discussion for another time.

 

On the under coat take it all off and start with a clean panel. No matter how far back you take it off it is never far enough.
Besides you may find rust under it that will need to be looked at and fixed.


On the fitment I cant say as I don't know the trucks and not seeing it in person, only thru pictures, I would not even start to say how to go.


But......how close is the replacement parts to stock? Are they the type to drill out the spot welds, pop the old out and new in and spot weld and done or do you need to trim the panels because they are oversize?
Are you doing this to look like it has never been replaced or something that will look good, not done in the back yard, and last and panel over lap is not a big deal?


The last what tools do you have to make this happen or are you farming it out?


I did floors, rockers, cab corners and rear door posts on my 81 F100. Drilling out spot welds where needed but also did some over lapping some of the floor pans to the old floor.
Only 1 side I did the other side also.

I also swapped the fire wall from anon-AC to AC


So I do know a little of what it takes to do this and had training in full body & fender work.
Dave ----

 

The floor pan goes UNDER the cab mount.

 

1. You need to cut/grind back all the metal that is so rusted that you can't make a good spot weld to it.
2. Most of the patches that I have received need to be modified to fit based upon how much metal you had to cut back. And occasionally the patch panel isn't long enough in some areas so you need to make additional patches. I use 16 ga steel that you can buy at Home Depot. Some of the guys on here use 18 ga as it is easier to bend. I wouldn't go any thinner than that. The floor support/cab mounts are available but there are lots of pieces of metal coming together there as harleyman's picture shows and lots of spot welds to cut out in order to make a clean install. It all depends upon how much of the metal is good in that area. I would avoid completely replacing that part if you can.

Front cab mount/floor support - A pillar

 

Had to bite the bullet..ordered new complete floor pan and fire wall..