I got mine from mojo. think they are out of stock when I looked last night of the 140mm conversion kit. I checked as I thought I had bought the wrong one.
I have an aluminium cup in the kit and I was looking for instructions to check where it went. Couldn’t find anything so will assume it goes at the bottom of the fork in-between the bumper stop and the plastic bit at the bottom of the spring.
Be good to hear how you got on; I’ve sourced the conversion kit from activesport plus the maintenance & seal kit. I assume you just pressed the seals in without using a special seal driver tool?