The alloy driveshaft may have an SYD on the slip yoke which will increase the weight. The alloy is 3 1/4" and the steel are 3" so the difference can be seen not only by the rusty steel of the silver alloy color. If the car is going to have the speed limiter removed like on XR's its wise to use the alloy shaft. The EL I6 Fairmont Ghia's didnt come with alloy but the V8's may have. I changed mine to alloy.

the car already has no speed limiter from factory..I really haven't had any time to confirm whether my old one is alloy or not, but i will confirm everything tomorrow with a magnet as mentioned..