I had been posting about this in another thread. This thread is specific to floor pan installation.
To begin, you need to grind the paint from the pan to determine where the rust stops. My floor looked good until I hit it with the grinder. Once the paint was gone I could see that the rust went further than I had thought. From there I took the new pan patch that I got from LMC, and set it in place and traced around it onto the floor so that when I cut out the floor I wouldn't remove too much metal, beyond the edge of the patch. If you have rust beyond where the patch will cover, then you'll need to add a separate patch. For that, use gauge 18 sheet metal.

In the photo above, you can see a patch I did beyond the edge of my pan patch.
Now you need to decide whether you are going to butt weld in the new panel, meaning edge to edge, or you are going to overlap the new pan onto the existing floor. The latter is easier, but water can get into the seal where the two panels overlap, and that will start the rust all over again.
If you are going to install the new pan edge to edge, butt joint, then set the new pan in place and make sure that it is absolutely where it is supposed to be. Once you're sure, trace around the edge and cut out the existing floor on the line. Then you need to grind all around both edges so you weld them together. Where the new pan meets the cab support, you'll need to drill some holes so you can weld the pan to the support.


In the photo above, you can see holes in a brace I made so I could spot weld to the cab support. You will drill holes through the pan and spot weld to the support.
Your pan patch is never going to fit perfectly. You are going to need to grind places, hammer areas, clamp places, and maybe weld in a patch on your patch panel if you mess up.
It is a complicated installation that takes patience.


If you need to make a patch outside of the pan area, begin by cutting a piece of thick paper in the size you need. Trace that to your sheet metal and cut it.
I used a white paint marker to draw lines on the metal to cut. The good thing about this welding project is that it will all be hidden beneath your carpet, so you don't have to grind all the weld as much as you would if it were going to show. Good luck.


White paint marker works great on black patch panels.
Good luck.

 

Thanks for sharing, staring down the barrel of this myself soon.

 

I needed a piece of 18 gauge sheet metal to replace a bit of my kick panel. I made a paper template and found I didn't have enough to make it. II went to the local home improvement center and they didn't have any. I tried Ace and they were out. Dang. I searched the garage and then remembered that when I bought my welding cart it came with a shelf that I didn't need. I finally found it, measured for thickness, and it was perfect. I'm so glad I didn't throw it out as I had considered many times. And, I saved $15!!

 

Yes, never toss any steel or aluminum - especially sheet metal.

 

I have saved a lot of things I think I can use. It has saved me a lot of money for projects over the decades........ But it does make keeping my shop organized tougher......

 

My garage doubles as a dentside parts store. Btw, I have a grill frame that I'm giving away. It has some scratches and a couple of small dents. Local p/u in So.Cal.
I wanted to add, for those considering doing this, it is a lot of work. The welding alone takes several hours. Then you have to grind the welds. The good thing is that you don't have to grind them perfectly smooth since they are going to be covered by insulation and then carpet. I'll also going to be coating the weld areas with a seam sealer to make sure there are no pin holes to allow water in. A tip: I use a thick grinding wheel on a hand grinder, 4 1/2", and that allows me to grind only the weld so that the surrounding metal is not ground thin.

If you're going to use a seam sealer above and below, you might want to think about installing the new pan so that it overlaps the existing floor. That will save you a tremendous amount of work.

 

I wrapped up the welding part of the job today. Then a ground the welds a bit and coated the welded perimeter with Por-15. Next I'll apply seam sealer, coat the under side with Por-15, and put the door back on so that I can continue with the prep for paint.

 

So today I finally got the brushable seam sealer delivery. I sealed the seams/welds inside, and went under the truck to do the same below, trying to prevent any moisture/water from entering and starting rust.




I think the only thing I have left is to paint the weld along the trans tunnel with Por-15. I gotta say that I like the paint, but man, if it gets on you, it's a bear to get off. I have spots on my arms that have been there for days, and I wore a long sleeve shirt while applying!

 

I did my frame in POR-15 and got a little on my hands. That stuff was on my hands for nearly a week. Great stuff though.

 

Today I got to the hard to reach welds under the truck and gave them a coat of Por-15. I also finished installing the Kilmat to the front of the cab. I still have 15 sheets to do the doors and the headliner. I think that I'll cover the back of the cab, below the rear window, with the Summit brand sound deadening sheets.

While I was under the truck, I must have gotten a small drop of the P-15 on my lip. Now I have to live with a spot there for more than a week. Unreal.



Area beside the cab mount bracket that I coated with seam sealer.

It was a pain cutting for all the crazy angles and curves. I did end up with more than a few small filler pieces added.

 

While I was doing the floor pan I decided to clean out the drain of cowl collection thing a ma jig. While cleaning it out with vacuum and the wire inside it, I found a hole. Today I welded up the hole and coated the weld with Por-15. Tomorrow I'll seal the welds with seal sealer.