Stick with your plastic body filler
I am restoring a 1941 Studebaker Champion coupe and am in the process of stripping the paint off of it. Where the top seams are formed there is lead filler that is deteriorating and falling out. An old-timer in my neighborhood told me that to do the job right, I would need to use lead again to fill it. Is this true? I am experienced with plastic filler and know how to work with it, but I have never tried lead. What should I do?
Most old-time body pros will tell you that they used lead in the old days because it was all they had. It is better for some applications such as places where there will be a lot of flexing and vibration and along edges of panels, but for the most part the modern plastic fillers are far easier to use and superior to lead in many ways. Plastic filler gets a bad rap mostly because it is so versatile that it is sometimes used in ways and amounts that were never intended by the manufacturers.
Lead is harder to master, and it too has its downsides. The metal to be leaded needs to be tinned so the lead will stick, and unless you get absolutely all the tinning solution off of the metal afterward, the paint you put over it will craze and crack. Also, lead is toxic and must be handled carefully. Plastic filler isn’t good for you either, so you will want to wear a particle mask while working with it. But plastic filler mixed and used properly, (no more than 1/8” thick when finished) will hold up fine.
Your car originally was finished with lead because plastic filler wasn’t invented until the late 1940s and didn’t come into common use until the late ’50s.
Which filler you use won’t make any difference in the appearance of the car. And used as intended, plastic will hold up as well as lead. The only reason I could imagine for using lead in place of plastic filler is if you wanted the car to be original right down to the unseen details.
My favorite filler is Evercoat Rage Gold. It costs a little more, but it is easier to use.