NEED HELP,FUEL PUMP BOLT ISSUE,LEAKS OIL

1968 Dart 270 said
From the photos you posted of the aluminum cover it appears the hole behind the bolt hole is smaller. Perhaps it wouldn’t go through and could be pulled out with a vacuum cleaner

I'm sure the threads go all the way through. The hole ID is smaller than the bolt od.

If you want to vaccume, bend a small ( about the same diameter as the hole) piece of copper tube into a J shape.

Attach the long side to a shop vac and insert it in the pump hole and line it up with the hole you are drilling and suck away!

Greasy gauze rag would be easier.

I think you are over complicating this.

Get-er-done