Spot welding panels?

[nkopper]

I'm working on replacing the rear outer wheel housings on my '69 Camaro while doing a mini tub. The question I have is about spot welding the new wheel housings in. Should I drill holes in the new housing where I want the welds and plug weld them in, or is there another way this should be done? I think that is the only way I will be able to attach the housing to the braces on top (inside the quarter, by the seat brace) since my quarters are still in tact.