L e d s tail lights on my 64

Just go to the local AutoZone / Kragen /O-really? / type chain store, and buy an LF12 Tridon flasher.

Two terminals, direct replacement. It will flash any combination of regular bulbs & LED's. It will flash 20 regular bulbs. Or one.

Only down side is you need to check your lamps on a regular basis. It will still flash with a dead bulb, so if you have a front out you will never know it. On the up side, the rear will still flash with a dead front...

B.