I'd say a steel 2 piece DS is the way to go if you're going to get it custom done. GM got it right with the steel 2 piece on the ecsb trucks. Mine's been to 120 the other day smooth as silk.

 

I looked into this and it's a no go for the new body style. The 2500 HD has it but the cross member is built into the frame!!! Also the frames are different between the HD and 1500. I looked to see if I could fab one up but you just don't have the room for it.

I do agree with you on this and the set up looked nice on the HD.
GM should have left a good thing alone with the two piece set up for the ECabs

 

my scsb 02 has a bad vib between 70-75 and my CC 06 is above 95 like you guys. One thing in common is both have been lowered. My scsb has a custom built high speed drive shaft from speed eng (I have converted to an 4l80e). I am swaping gears and will be checking pinion angle tomorrow and let you guys know how it goes from there.

 

well, this has been encouraging. might as well leave the damn speed limiter on. my truck has a 3/5 drop. steel drive shaft, and no pinion shims to my knowledge. i havent experienced any vibration so far. i had a tune planned in the future, but why bother. these trucks seem to turn into money pits when you start modding them.

 

I have the same vibration after 90mph since the day I bought my truck. I've tried everything besides getting the drive shaft balanced. For now, I just don't drive over 90mph, when I have my TrueTrac and 4.10s installed, I'll have the drive shaft balanced then. I will need to get it done before any other mods because I'm at 91mph in the 1/4. I sure wouldn't want to sling a drive shaft at 90+mph. I'm even thinking of installing a drive shaft loop.