I have a Wilcox Crittenden 4042 "Winner" (Type 4) Head - and the cup leathers are worn out and they don't seem to be available anymore. Can anyone help? --- Either help in sourcing the parts, or in getting the specs?
Might not work for your needs, but pump leathers are still made and used for water pumps. Google pump leathers or cup leathers etc. Find the specs by measuring the old ones or the cylinder. They can be trimmed to fit. I did this for my galley pump.