I have researched and found the site with the info. Appearantly, from what you are saying, there must be two hydraulic cylinders on the truck. When they referenced the "clutch cylinder", I assumed there was only one and mistakingly called it a master cylinder. I have owned several vehicles in the last 38 years with hydraulic clutches and none had more than one hydraulic cylinder. They all had mechanical linkage from the cylinder mounted on the firewall to the pressure plate. The hyd. cyl. operated the mechanical linkage. Similar to you, I have been re-building and restoring vehicles for 40 years.
If someone can tell me how to put the link to the other posting, I will do so. I have never been able to find any info on how to do that.