Biggest draw backs of using scrap sheet metal is going to be your time, effort, and welding wire. It will take a
ton more time to make patches and get them to fit using scrapped sheet metal than if you use a pre-made replacement or patch. The replacement panels weld in with spot welds like the originals. Home made patches won't follow all the stock panel shapes, so you'll have to run a lot more beads than spots. I have done both, I've made patches out of plain old sheet stock and I've installed full replacement panels. Even small patches take a lot longer than a large replacement panel because of the amount of welding and shaping that has to be done.
Next in line would be the repair looking original. Obviously your scrap sheet will not have the same stampings as the originals. On a '75 this is less of a concern, it would be a bigger draw back if the car was worth more in original form. But consider that if you ever sell the car to a well versed buyer they will figure out the repair was done with scrap sheet and not an OE stamped replacement, which could hurt value. It's like looking at a Mopar with the engine compartment painted black instead of body color. It doesn't hurt the function any, but it raises a flag- "well if they did
that, what else did they do?"
And don't forget that welding gas and wire cost money too.
This is a perfect example. Even with the OE stamped panel replacements that fit well, it's arguable that replacing the whole pan is easier. Look at how much weld is there! Just to replace the front footwells like this you have to remove about 30-40% of the spot welds that you'd need to remove the
entire floor pan, even though you're probably only replacing 20% or less of the metal in the floor. And then you have to do a significant amount of cutting, followed by a bunch of long continuous weld beads.
For me this is the breakover point. If I have to replace any more metal in the floor pan than what is shown here, I'd do the whole floor using an AMD replacement. Yes, it's more expensive for the whole thing. But all it takes to remove is a spot weld cutter, and all it takes to reinstall is spot welds. And when you're done the whole panel is brand new and rust free. You spend a lot of time running long continuous beads on sheet metal, use a lot more gas, and a lot more wire. I understand being "money poor" and "time rich", but there's always a breakover. If it takes years to finish you might have been better off saving longer and spending less time on it.
1974 PLYMOUTH DUSTER Auto Metal Direct Front Floor Pans 400-1267
