Shower liners for sunken showers

We are just beginning to think about upgrading the original small bathroom and adjacent wash room that serve the master bedroom. A recent article In "Eichler House of Questions" brought up some excellent considerations and implications related to changing the configuration of a shower, mostly plumbing related. Additional questions that I have are as follows: What type of shower pans were typically used in the small sunker Eichler showers, and are these same shower pans available as standard purchases? Also, if these are not standard available items, of if the configuration of the shower is changed during remodel, what shower pan method is typically used for sunken showers, slab on grade construction? Thanks in advance for response!