2116 and other old memory chips

I am in the process of attempting to repair, with Pete Turnbull's invaluable guidance, an Exidy Sorcerer. The manual recites that the memory chips, depending on configuration, are 2104 (4k) or 2116 (16k). A casual perusal of chip sources shows that most begin their dynamic ram sections with 4116 chips. The only mention I have found of 2116 chips is in a reference to the original IMSAI memory board. So, my questions are: Are 2116 chips 3-rail? Are 4116 chips equivalent? Does anyone have a source for 2116 chips, if they are not equivalent? What about 2114 static ram (used in the video section of the Exidy)? Same problems? Were they all three rail? A general lecture on the nature of old memory chips and their use and selection would be very helpful (hint to Tony Duell). Thanks, Louis