I have a Swap Meet Next weekend also.
Here is what I have to share about spot welds.
I tried the ones like Hf has.
https://www.harborfreight.com/38-in-...ter-63657.html
The ones I got from E-Bay are the Ticket.
This is just an Example link.
Link:
https://www.ebay.com/itm/38677284736...3ABFBMrtz6ybhj
It is best to use a small Starter drill.
I use sandpaper or scotch-Brite to determine the center.