Courtney,

About your [bus's ;)] sagging rear end (I, too, have a '78 T2).  Oh, but
I wish it was as simple as new shocks.  The simple answer is that shocks,
be they gas or air, won't help your stance at all.  The trouble is in the
torsion bars, which after years of hauling that mighty 2000cc powerplant
(GOD, I love to be sarcastic late on Sunday nights!) is now just losing its
tone and firmness, like ourselves.

Shocks will only give you greater clearance from the point at which the 
torsion bars sit.  Therefore, new shocks will give you a better ride on a 
bus that's STILL sagging.  To fix the problem, you're gonna have to get
those torsion bars re-adjusted, and yes, it is EXTREMELY time intensive.
I am currently saving my $$$ to pay the labor fees to have mine done.

Bummer, the easy way out ain't gonna do it this time!

Kurt