Roger,
I've used both the type of bulbs that you showed above and the ones like Mark K posted. I would recommend going with ones like Mark posted because they have side and/or rear mounted LEDs that fire back into the reflector of the tail light. That's really where you want the light to go for the tail light to be the most effective. The lights will appear much brighter to drivers behind you that way, both at night and during the day.
I bought mine from V-LEDs.com. They sell the bulbs in pairs. They're very bright, and are great products. I have their red ones in my tail lights and white ones in my backup lights.
The flasher that Mark posted is also the one I bought when I converted to LEDs. You can probably find these at your local auto parts store for ~$15.