PCM is not related to having multiple model memory or programming (other than fail safe).

It is a coding method for the signal that is sent to the receiver. All Futaba PCM transmitters can transmit in PCM mode or PPM mode. If you want to use PCM receivers, you MUST use Futaba. No other brand will work.

If you use PPM, any negative shift PPM receiver (often incorrectly just called "FM") will work.

Is your current Futaba receiver model RxxxDP or RxxxDF?
If it is RxxxDP it is a PCM receiver. RxxxDF is PPM.