Headlight bucket fasteners?

I'm putting my headlights back together and I was planning to use three M5 cheese-head slot machine screws with flat washers and nuts to attach the headlight bucket to the body.
I noticed the ones used previously are not metric, so I think they've been replaced.
Can someone tell me what was used originally?
I've seen everything from speed nuts to dome-head machine screws on these so I guess they are all replaced with whatever was handy over time.

thanks, Andrew