Clean the groove out squeaky clean.
Sometimes there are places around the rim of the hole where they have been staked (mashed, as we say round chere). You will need to fix those areas.
Put the cap in place and strike the center with a hammer.
You can stake around the rim several times with hammer and small punch if it will make you more confident in holding it in place.
Carl


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission