Crusty54,
1st off, Welcome to Stovebolt!
According to a couple different Chevrolet Master Parts Catalogs (1954 and 1957), the "turn signal assembly with cup" was offered as a standard part under Parts Group 2.895. The 1954 book indicated GM# 897334 (applied to 1954), but the later 1957 book indicated GM# 897125 (applied to 1954-55 1st Series).
You might want to check this old thread
concerning the turn signal assembly that is a bolt on for your truck.
I recall a more recent conversation not long ago about this, but couldn't locate that particular thread. Perhaps another Bolter can point you in the right direction???
Anyhow, the above linked thread does provide additional info on things you will need beyond the noted switch assembly to install the unit your mentioned.
Dan
