While searching for the input shaft shims I found most were on back order and high priced (over $10 per shim) so I looked on dabay and found some for a $1 each. The shipping date was about 2 weeks, a week longer then the others.
New old stock (NOS) shims from Spicer that traveled half way around the world and back to my home.
Volken was surprisingly easy to deal with.

New 4.1 gears installed


Overall the swap was straight forward with patience and attention to detail the job is fairly easy. First, the advance adapter’s D300 4.1 kit instructions are absolutely worthless which is a surprise because their D20 3.15 installation instructions I used last year for my 20 case were excellent. I instead used Lomax 4.1 kit installation instructions that were easy to follow.
If I had a choice between AA or Lomax on 4.1 kits I would choose Lomax for a couple reasons. First the AA came with no directions (let qualified mechanic install gears) and the price, as of today the AA kit sells for $705 and the Lomax at $450. The AA kit I installed came as an extra on a Jeep deal.
FYI,
Torque specs Ft-lbs
Bottom cover bolts = 20
Cover plate bolts = 35
Output yoke nuts = 120
Bearing caps = 35
Shift fork set screws = 15