Ah yes, the flasher conundrum!
The flashers in our cars flash at a rate that is directly proportional to the amount of current that flows through them. By changing to an LED bulb, the current draw is greatly reduced, therefor the flasher unit won't!
The short answer to your question is that ANY flasher designed for that smaller, LED current will be fine.
The only consideration for our OLDER cars is the polarity. Unlike light bulbs, LED's are polar which means that the direction of current flow is imperative. If you have a positive ground car, you'll have to swap the wires at the bulb socket. Other than that, electrons don't care if they're flowing in a 68 Sprite, 72 Pinto or an 09 Jaguar!
On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"
'68 Sprite 1275
'76 Midget 1500