The early 180 IPC shows compression spring p/n 3222, which is 0.036" or 0.042" thick depending where you buy it from. In the mid-1960s they switched to a p/n 3432 spring, which is 0.060" thick. Any idea why they changed compression spring part numbers?

In addition, I see the Cessna service manual showing one shim/spacer on the inside of the spring and the other on the outside but other diagrams showing both on the outside.
What works best?