Another turn signal question...need advice from electrical guru

[mcgarrett]

Installed a period correct turn signal switch in my '40 Ford and wired it in front to work my park lamps as the signal lamps, and then spliced into the stock tail lights. 6 volt system using 6v bulbs and flasher. This setup works fine except they don't flash at the rate we are accustomed to seeing - the interval between the pulses is very short and the flash rate is very rapid. Anything I can do to slow it down to a more conventional flash rate? Is there something in the circuit to check that might be causing high resistance? Any electrical experts out there with some sage advice?