Speed compensator vs. Speedo gear?

[5.0PiMpin]

was up guys, i just had a real quick question regarding the difference between a speed compensator and a speedo gear. i just installed 3.73's in my ride and i was told two different things. ford told me to get a speed compensator that connects to the speed sensor of my vehicle and every body on this web site told me to change my speedo gear? for one i dont know where the speedo gear is and i dont know if it is a job that i can handle my self. the speed compensator runs about 149 dollars and i dont know how much the speedo gear is going to run and how difficult it is going to be to install. i love doing my own work on my car but only the things that i know i wont screw up. if any body could clear up this mystery for me i would greatly apreciate it. thanks

danny