Can I Spot Weld

I'm replacing the door bottoms on a 47 Ford PU. The outer panels I bought are made with a lap joint to the existing door panel, where the new sheet metal goes in behind the existing by about 1/2 inch. My question is , if I drill say 3/16 inch diameter holes an inch apart in the existing door sheet metal then spot weld through these holes to the lap joint metal is this good enough , or should I spot weld the entire length of the seam? I'm not looking for show quality , but I also don't want the body filler to crack between spot welds . Thanks , John

Ive done what you say and used fibreglass filler along the joint so the final bondo coat doesn't crack.

Solid welding is always preferable but seeing how it isn't a butt joint I agree with EnglishBob. Us e the short strand fiberglass filler, then skim coat of Bondo.

I use the short strand fiberglass filler over all of my welded body panels seams as that with my eyesight there are always pinholes and it helps to seal up the weld.
Torchie.

I agree with what the guys have said. Kitty hair fibre glass filler.

Have a look at how I made the temporary reinforcement to chop the 49 Ford truck roof. This might work to keep things lined up before you cut and while you weld and save you work and body filler after you are done the metal work.

The ideal way would be a butt joint, but I can tell you that working with a hammer and dolly after is pretty difficult in this area. You gotta be a contortionist to gart in there and swing a hammer at the same time.

most vehicles have a spot welded lap joint EG: quarter panel to roof sections. I would seam seal the back side of you are going to do it that way. This is so moisture can't creep in from behind and start it rusting. A continuous welded butt joint is best but you can do a spot welded lap joint without to much trouble.