But I have a Futaba 3PJ Super from the late 90's, the manual says it has an (8) model memory.
The FM/PCM has a failsafe/throttle cut, so I bought this with a Kyosho USA-1 Nitro Crusher, back then.

Didn't notice that mine is the 27 MHz FM/PCM band:

- and when I went and tried to order the same Rx model number FP-R113iP I already have, which is 27 Mhz:

I accidentally bought the 75 MHz instead.

Regarding 27 MHz:
When I went looking for the 27 MHz FM Rx Channel 4, crystal, that I would need to match my Tx, there were very few 27 MHz crystal choices, at all, whereas the 75 MHz FM crystal selection seemed to be much larger. Is that possible, that there is a wider selection of 75 MHz crystals, than 27 MHz?
Ultimately, I would like to have more than (1) car on the Futaba 3PJS, but would I be better off finding a Tx module for the 75 MHz band, in order to find a matching set of (3) crystals?
Hope any of that made sense. Thanks!