i dont know if LEDs will be bright enough unless you are forking out for the superbright LED clusters used in new trucks/bikes and stuff which are very expensive. Normal yellow lense plastic utility flasher lights would be way cheaper, and there are a lot more types around.
As for the wiring. Mount the lights. I assume there will be 4. 1 at each corner. One of the wires for each of the lights, doesn't matter which (if they are standard bulbs) you just screw to a ground point somewhere close to the light, or you can run to a proper ground on the battery or somewhere. The other wire from the lights you run to the output pin of the flasher unit. It usually has 4 pins I think.?? You need to run power through a fuse from the battery to the + on the flasher unit. Ground the -switch wire of the flasher. From the battery, and maybe through a fuse (main car harness somewhere maybe), then through a switch run the +switch wire to the flasher. And that should be all there is to it. There are many basic variations on flashers, but they will all work on basically the same wiring structure I think.
Sam