first gen master cylinder reservoir filler hole cover ?

are these available anywhere  ? when it's cold outside that wind coming up thru that hole   

I'd be surprised if that is available....... You could either make something or..... get a screw-out deck-access-plate from a marine supply like West marine.......It's a beveled screw-down ring with threads inside and a screw-in lid.....They are intended as waterproof access ports for boats, so they have a rubber o-ring and are water tight... They are available in different sizes and are perfect for access anywhere you just need to get your hand ie; radiator cap, dipstick, etc......There are even versions with a clear lid if you have something where visual monitoring is a need....

There are round covers like that used on three or so different GMs and Fords in the 50's and 60's.

I don't think anybody has tryed to find a match to the first gen.

M1D

Big thread on this over at VCVC, no one has found a replacement plug from any vintage car GM or other that fits perfect, just make one from something, a couple of pieces of 1/4" rubber sheet, a larger piece on top to fit the lip will work fine, a plastic paint can lid, plexiglass disc, the boat plug mentioned, etc...be creative. If its under carpet or a mat, no one will see it...There was talk of reproing them or a 3D printer making a plastic one but it went nowhere....

I used a round elec. box cover

I used sheet metal.

I remember the original plug on my 66 as being thick above the floor, a real pain to stuff into the hole and not easy to get out, unless you wanted it to stay in.... I can think of half a dozen better ways to securely cover the hole, several of which wouldn't require drilling any holes in the floor....

I put some KY jelly on mine and now it slides in and out real nice...

bletman wrote:

I used sheet metal.

Perfect, all ya need! Did you put a gasket under it?

Yes - I cut a gasket from and old bicycle inner tube.