If you use the linked below flasher made for LEDs, you can eliminate resistors. I've used all LEDs in the signals, and now use conventional tungsten based bulbs up front, and LEDs in the rear, and have never had a problem and have never used resistors.

I believe the FL 3 is the one we use.
http://www.superbrightleds.com/cgi-bin/s...%2Fflashers.htm
If you go this route, I can verify the flasher model if need be.

I see they now put mounting tabs on them. Mine didn't have the tab, but if it did, I'd lop off that rubber falls apart mess the factory installed, and zap screw the flasher to the frame.

FWIW - when the supplier above states their LEDs are bright, they aren't kidding. Good products from there.