After years of ridicule from friends and family alike, I finally got my first mustang a 90 GT 5.0. It's got 150grand on the motor. It runs pretty strong, leaks nuthing, burns nuthing, runs cool. It's an auto and sometimes it doesn't shift properly while cruising, but shifts fine when I get on it. Any idea what this could be? Also, can I do an h/c/i combo with so many miles on the motor, like I said runs strong and quite(except for the exhaust). And is there a way to find out what gear ratio I have? Thank in advance, you guys know your **** on here.