I am replacing the rear part of the trunk floor on the '76 car. Did it with the 3.2 build too, so I thought it would be easy. But, it isn't. Sorry, but the camera is at the workshop, so I have no pics. However, the basic problem is that RD makes a pressing for the 70-74 trunks, and Porsche changed bumper design and thus the trunk floor shape for '75 and '76. First step was to hammer out some of the ribs in the new piece. Next step was to start forming the panel to match the original, next step was to hammer out some of the creases that I put in the wrong place. Next step was to anneal part of the metal because I was worried about work hardening. Et cetera. I am closing in, but will not be able to metal finish away all of the hammer marks. I am not that accomplished.

However, I have leading supplies and the piece can be laid flat! So I won't be dripping lead down the fender as I have in the past. On the other hand plastic filler is less toxic and very simple to use. Furthermore, I am not going to park the car in the rain like the previous owner did and the trunk looked fine until I started stripping the paint off. So filler is pretty fantastic stuff.

Any opinions?

I'm not a body man/expert but my $0.02 is that unless it's a "necessary" use of lead, for something like a high$ resto, I'd assume modern fillers are more than adequate and probably easier to work with.
Let us know what you decide.

Spot putty should work on hammer marks. Maybe get a new hammer. Sometimes the edges are too sharp.

I tend to believe that there is no need to apply lead to a vehicle and location that had not previously been leaded. Perhaps a glass-stranded filler, (overlayed with a final coat of bondo (Rage)) would make for a good base if you are concerned with fill toughness in the more damaged area. Fiberglass filler is my go-to for such a repair.

Keviin

It depends

Pics will help offer some better answers

Yeah. I know. Pics in a day or two.
I am trying to do my best work, so that is one reason for asking. Is lead filler somehow better in people's eyes?. The piece from RD has a beautiful zinc finish that should make the leading easier. I like trying new stuff, and plastic filler has gotten old. And as mentioned I can lay the piece flat.
Thanks folks!

The RD pieces are galvannealed. I always grind to bare metal the area to be welded but don't know if you'd want to leave it or remove it if you do opt for lead. Maybe someone knows or a call to RD...?

Lead can be applied in any position, it need not be flat.

Lead tends to be more forgiving on seams that are prone to flexing which is why it was used along roof seams and fender seams back in the day. Modern reinforced fillers have largely eliminated this concern.

There's a seam on the 911 rocker that needs lead. If you use filler, it cracks. When I worked at the shop, the guys preferred body plastic but used lead when needed.

Many positions by some, flat by many. In my initial forays gravity didn’t seem all that friendly, although I have never leaded in outer space. The zinc would be expected to play really nice with lead. Didn’t know about the flexing. Nice to know. Looks to me that some subassemblies were put together and brazed prior to the spot welding. I do like brazing, and may do some of that as well as this poor fellow gets closer to the road.

If the lead is liquid and running off, too much heat.

It should be manipulated with a paddle that has tallow on it when it’s in a soft putty like state. Easy to move around like mud but defiantly not in a liquid state that will run off a vertical part.

Lots of good YouTube videos out there. After that it’s just time with a torch in hand.

We used lead on the fender, where the doner butted up with the original. It's a good way to go, if you have some one who knows what they are doing. It's becoming a lost art and the old timers that know how are truly a site too see when they are applying their trade.
If you don't know what you're doing, it can quickly turn into a cluster and down the road you will have issues for sure.
Fortunately, I had my dad to help out. He's been doing lead work since the sixties and understands it. Most are not that fortunate.
I have some (a few) of video clips I could send along of my dad doing the lead work and metal filing if you're interested. Just have to figure out the best way to display them. Let me know.

Worn, there are body fillers/plastic panel adhesives that are tough as nails. Best, Mark

I know Mark, and thanks. Mostly I like to try new techniques. I have wooden paddles and the lead and the flux, so I really was wondering how people felt about the idea. People say that I should buy a Cayman and I know they are right. How are you liking April so far?

I have done body work as a hobby my entire life. My uncle still does paint work for a living in his 60s and has never used lead. So lets put a number on it like 30 years or so for me. Painted about 10 cars so far .. The plastic fillers now like Rage gold are amazing. The one thing I will tell you is my 77 firebird(my 1st car) used lead to blend the roof and the 1/4s and the lead cracked on my car and it was pretty much a standard on firebirds and camaros..

In my opinion I would never use lead because of safety. Also keep in mind that primer surfaces are basically plastic filler in spray form so what really are you"gainig" but using lead?

Useful under powder coating where high cure temperatures won't allow use of plastic filler. A little off topic w.r.t body work but worked well for engine tin.

I tried Lab Metal Hi-Temp but had better results with Lead. The Lab Metal swelled and was quite noticeable after powder coat.

I did learn an important lesson. It was to not allow my powder coat shop to do the sand blasting . They still managed to leave some "shadowing" where the sand blast added texture to the soft lead that I didn't anticipate. Next time I do this, I will do my own sandblast work prior to powder coat.

Before Lead:

Click to view attachment

After Lead:

Click to view attachment

For that I can see it.