The 54/55 do not use the brass nut they use pan nuts available at about any auto parts store. If you put the smaller brass nuts on them you will strip them. These were in common use by GM in the 60's and 70's for things like emblems and lights.
Agreed,they did not come from the factory with brass nuts but using them makes the job easier. You must have powerful fingers if you can strip 1/4-20 brass thumbnuts with them.
