70-72 Side Mirror Gasket

[Shortbox MoneyPit]

Hey guys, I searched the threads and couldn't find any info on this. I just bought a new set of 70-72 side mirrors and found a good way to mount them, but the black gasket that goes btw the door and the mirror mount seems tacky. Do most guys use this, or do they mount it directly on the metal or use some other type of sealant.

Also, the old holes from the previous mirror (the doors were from 67-69 with the other mirrors) are still there but covered with the new mirror. Should I try and weld the holes shut or use some type of rubber sealant so it doesn't leak into the door. FYI: my welding skills are coming along, but not great right now.

Thanks for the help in advance

Shortbox MoneyPit