I have a wide selection of Mopar 1 piece driveshafts that are well over 60" long. In fact, its pretty difficult to find them under 60" long. Longer driveshafts are simply a larger diameter. I have one out of a van that is over 72" long, but its about 4" in diameter. I have a 62" long driveshaft I built that has spent many years under a few big block dirt track cars. A longer then 54" one piece driveshaft has never been a problem. Gene