Woo Hoo

I'm working on rebuilding my mid 70's Motobecane. Still in very good shape. Since I've long since lost my bike shoes, would prefer to get the newer style pedals and clips(?). What are the odds it's a 14mm thread, and how can I verify that just running a 9/16 tap will allow me to use a new pedal?

The rebuild process has not gone nearly as well as I would have liked, my local bike shop has screwed up more things then they have fixed.