I just spent a couple days reading up on this and placed an order with superbrightleds.com last night.
First, the answer to your question is no, the mechanical flasher will not work. You can get an electronic flasher at most any autoparts store.
Based on what I read replacing the flashers wasn't worth it. They aren't used enough to justify the cost of LEDs, in my opinion. I did get the 22$ rear 5 watt. That, coupled with colored LED's through the whole cluster, and a relay on the headlight will make life easier on my charging system. I also got a RearAlert off ebay to flash the new brake LED, so I don't expect to get rear ended anytime soon.
I would like to replace the front running lights with 3 or 5 watt LED's, but that's for another day & paycheck.