I should have gotten this info out weeks ago, but i
have had not had a chance to even look at my e-mail,
let alone write any, it's been so busy.  (I owe e-mail
responses to a bunch of people...sorry!)

The rear spring shim is roughly 6" in diameter with a 1
3/4" hole in the middle.  I used on 3/16" thick to
level.  1/4" should be fine.

The front spring shim is roughly 5 1/4" - 5 3/8" in
diameter.  It has a large 3 1/2" hole in the
middle...so it is like a big washer that is about 3/4"
wide.  I used a spacer 1/8" thick to level the van.

Use at your own risk!
Steve