So, some interesting replies ...

1) Sorry, I meant the relays - but everyone seems to call them flashers.

2) I have one of each square and round - turn and emerg

3) the mounting brackets accept both but fit the square ones better

4)
Quote
Originals are all round, never saw the square ones until the 1990's.

this is an interesting statement because I've owned the car since '73, never changed a relay and the car was mothballed in '85. So I'm pretty sure the square one is original.