Yup, they sure do lengthen the driveshaft. Like AZ said I'm running a super shorty SYE and I love it. The output shaft being shorter and fatter makes it stronger than any other on the market in my opinion. My Dshaft is probably 6" longer than stock and 3" longer than a standard SYE. Yeup it does use a tone ring and and electronic sender for the speedo calibration, but honestly if you have the right gearing for your tire size then the difference is minimal. However there are people that use the True Speed calibration tool from Superlift to cure that also.