RE: futaba 8 channel
If your transmitter was originally on channel 60, and you changed the crystal to channel 38, it's possible that the transmitter is now out of tune enough that the receiver's not getting a good signal. To clarify, your transmitter module may need to be tuned...or it's the receiver that's off, and you'll need to get it and its transmitter tuned. Without putting them on the proper test equipment, there's no telling what might be wrong.
Any Futaba FM-PPM receiver will work with any Futaba FM-PPM transmitter. Any Futaba PCM1024 receiver will work with your 8U-series transmitter. The Futaba R127DF is an FM-PPM receiver, so you'll have to make sure that your transmitter is transmitting in PPM mode.