Been doing some research to refresh my memory today since the current master/slave has been in the truck for two years.
Speedway had good documentation for their slave cylinders (which look exactly like the eBay one above) and they recommend using a 3/4 bore master and a 7/8 bore slave with 3/16 hose. If you want quicker clutch action, use a 1/4 hose.
Looks like it has something to do with volume of fluid - ie, small (3/4 bore) pushing large (7/8) or vice versa.
Factory Ranger master cylinders are 3/4 bore, and my Toyota slave is 3/4 bore so I believe that is my problem. Will be ordering a new slave shortly.