Ford Repair: Mustang speedo adjustment, speedo gear, oversize tires

Question
Hi, I have a 94 mustang gt , 302, 5 speed, with 17" oversize tires, the speedo is way off , if I'm going 55 it says I'm doing almost 80 mph, how do I go about fixing (correcting this), is it a speedo gear or all eletronic, thanks in advance

Answer
Paul-

  That's a bit odd, as bigger wheels/tires should make it look like you're going slower, not faster.  In any event, I believe the '94s still had a mechanical speedo so it should just involve swapping out the speedo gear on the tailshaft of the transmission.  Hope this helps.

Steve