The Delrin "spacer/mounting" blocks are locally fabricated and/or "sort of" available from Amel. When I ordered a couple of sets from Amel to replaced my cracked ones, they arrived but I quickly realized, that on my boat SM #335 at least, that the top and bottom spacer/mounting blocks are NOT identical. They are mirror images of each other (as noted by ligning up the mounting bolt holes in the gearbox and the "flats" where they attach to the mast. I couldn't seem to make Amel realize the predicament and their error even with detailed labeled photos. SAV insisted they only had the one piece, all identical, and not mirror images (i.e. a top and a bottom part) so as to match the mounting holes. I solved my problem by drilling new mounting holes to match the holes in the gearbox housing.
A modification I made, while I was at it, was to mill a drain channel in the bottom surface of the top spacer/mounting block so that water, that accumulated in the top of the gearbox in the reservoir created by fitting the spacer/mounting block, could drain rather than puddle.
All the best,
Gary S. Silver
Amel SM 2000 # 335
Puerto Del Rey Marina, Puerto Rico