Most likely you are referring to a pickup truck?

There was no factory rear "splash apron/shield" on 47-55 pickups.

Patrick's (I think) has made a very nice aftermarket splash apron for 47-53 pickups (sold by Patrick's and by most reproduction parts vendors).

That 47-53 splash apron/shield does not work on a stock/standard 1954 pickup truck (I know - I bought one from a vendor who mis-listed it as 47-55 - I tried - I sold it).