Here is a small pictorial on front floorpan replacement on a '65 Mustang fastback. There are several ways to do this, but I used the overlapping/plug welding method on this car. This was a race car, and the owner was not concerned with originality. Butt welding the pan to the tranny tunnel and toe board would have also added several hours of labor to the job, as I TIG weld anything that is butt welded.



The floorpan had been replaced with a piece of sheetmetal and was crudely done sometime in the past:











The easiest way to get the floorpan out is to mark lines with some chalk and cut it out with a cut off disc on a 4 1/2" angle grinder. Keep in mind that the frame rail, tranny crossmember, wiring and fuel lines are underneath the floor pan, so mark accordingly:











You may also find the need to use a Sawzall for the corners:







The cut off wheel will cut through the sheelmetal easily. I cut out one section at a time as it is easier than trying to remove the entire piece at once:



















The pieces of the original floorpan were still attached the the frame rails:







Rather than use a spot weld cutter to try to cut through a dozen or more welds, I use a grinding wheel on the 4 1/2" angle grinder to grind through the metal to get to the frame rail:







I also grind through the metal where it attaches to the rocker panel. Take your time and go slow, and the metal will practically fall off leaving a nice clean surface to weld to:







The frame rail can also be cleaned out of any dirt at this point. This is also a good time to pound out any dents in the frame rail:







The new floorpan can now be measured and trimmed to fit:







The Beverly Shear knock off sold at Harbor Freight trims the excess easily:







The new pan fits really well. Now is the time to use a good quality weld through primer on any bare metal that will get covered with the floorpan:







The holes for the plug welds are marked and drilled at this point. I use a drill press:







The pan is set in place and sheelmetal screws are used to clamp it down. The holes for the screws can be welded up after they are removed:







The holes are now welded closed:







I stitch weld the floorpan to the rocker panel rather than plug weld it on the bottom side:







Some body caulking along the seams, and it is done. I have six hours in the whole job:

 

This is an excellent write up! I wish I had seen something so detailed and really done in the DIY spirit. Thanks Falcon!

 

Where were you a couple weeks ago when I did my 69 floors. Yours look great. Honestly, I had a hard time plug welding. Thanks for the pictures - they help us amateurs.

 

Nice job. I really don't miss doing that kind of work. I'm glad I'm past that point......

 

Looks great!
Let's see what the underside of the new pan looks like all around.
Lynn

 

nice write up

 

i like the idea of sheetmetal screwing it on. Always had a hard time with those clamping pliers etc, tackwelding etc. good idea. nice article (as always!)

 

If you are going to have an overlap, I would recommend weld through primer on the lap, and epoxy before and after the seam sealer. Rust will start and be hidden under that lap in a big way.

 

I used the weld through primer on all the hidden areas. The car is going to Phoenix, so rust will not be an issue.

 

Very nice write, bookmarked it for future reference.