Ok, it will never be air tight but...
This is what I did for the steering, brake, and clutch. I use Ace Hardware 1.5" x 1/16" neoprene washers. The two plates make adjusting the washer easy. The firewall plate side has 1/8" think foam tape. I used U nuts so I can finally not strip the holes or have loose panel pins. Lotus kind of hacked the hole making the plate larger but it works.