According to Year One and Firebird Central, the OEM Delco switch is the round one. The '69 and up is the flat one. Then there is the Boyne [never heard of it ?] style which uses a round 4-way flasher hole in the column. The Delco has the 'D' shaped hole. Now, is there any difference between the standard and tilt column switches? Because I see both being advertised. I also see column and floor shifted versions. Yet they all look exactly the same.