You can go with the 6 Ohm/50w resistors, but you will need 1 for each turn signal (4 total). If you get the 3 Ohm/50w resistors, you will only need two (1 for each side). These can be mounted in the front or back, it doesn't matter. As stated above, just buy them online, and you will have them in a few days. I use this website:
LED Flashers Blinkers Resistors Load Equalizers for Turn Signal Replacement Bulbs Rapid Flashing Fix
Hope this helps!