If the 8-channel transmitter is one of the Futaba 8U-series transmitters, you just install the 8-channel TM-8 module and you can use any Futaba FASST aircraft receiver. Each receiver will need to be linked to the transmitter at forst, but they will always stay linked to the transmitter. So if you use different models that are saved in the transmitter, each one that was previously-linked will still be linked when you change models. You don't re-link each time you change models.

However, any receiver that's linked to the transmitter will operate if it and the transmitter are both on, even if that receiver is installed in a different model than the one selected on the transmitter. That's just the same situation we've always had with the older R/C channels.

If your transmitter is an older 8-channel unit, then it will not accept a modern TM-8 FASST transmitter module.