Where are you ordering the LED's from. If ebay, do you have a favorite seller?
Also would I need 2 of the NAPA electronic resistors for left and right sides? What if I only want LED in rear, would that NAPA resistor work properly?
I did buy some LED's from ebay, some were good, however the 1157 tail/brake light ones didn't work very well. The difference in brightness between the brake light on and off wasn't enough to be safe. I ended up taking them apart end replacing the internal resistor so that the difference in intensity was better.
I got my first batch of LEDs from ebay, can't remember the seller but he was from Hong Kong with free shipping. Now I order my LEDs from either SuperBright (a sponsor here) Super Bright LEDs ? LED Lights, Bulbs, and Accessories
or AutoLumination www.autolumination.com Tail Light Brake Light Turn Signal LED Bulbs
As far as the Load Resistor goes, don't let yourself get confused between the flasher and load resistor. If you want to replace the flasher (recommended) you just need one, no matter how many LED signal lights you install. If you go the resistor route, you need 1 for each the left and right signals. Depending if you install just rear led signals or both front and rear on each side will determine what size of resistor you need. 6 ohm for 1 light, 3 ohm for 2.
The Electronic Flasher unit I bought at NAPA is a model EP-34 made by Tridon. It says LED 2-6 lamps right on the unit. I'm sure you can pick up the equivalent unit at any major auto parts store. (Pep Boys, Autozone, etc.) Its a standard Japanese 3 connector electronic flasher, just confirm the connections and it needs to be about 1" square, the round ones won't fit in the connector housing. Make sure you specify Electronic or LED Flasher Unit, not a standard thermal unit.
Viewed from the bottom.
Just a note... when you go to remove the flasher from the car, the first time you try to remove it it will be very tight. Just sueeze in the clips and wiggle the unit back and forth as you pull it from the socket.