[U]Denny: With short driveshafts it is very important to have everything inline and no offset at all.
You will need to install a rear end that has the pinion in exactly the right place to allow for a straight line from pinion to trans.
Thats what I was talking about.. Your diff is "above" the center line. With a short shaft you could be setting yourself up for shakes.
I get rods in that have a offset side to side since the 8.8 is so popular and most of them are fine.
It's the up and down I worry about.