perhaps a dumb lift/vibration question...

[dman1982]

got a 84 k10, did a LS swap to it, running the 4l60 trans with a 208 case, running 4.56 gears with 35's, and a 4 inch lift, i went through the forum so i may not have to bug anyone, but i was talking to a buddy of mine cause i get a vibration at higher speeds right around 70-75 and even more when i let off the throttle, he was telling me i may need a longer drive shaft, right now its a aluminum one out of a camaro/trans am, much light than the stock one, but the same length as the original one....just looking for the cheapest way to fix the issue, was thinking there might be a driveshaft from another pickup with the same u-joints just longer...