Help. I know almost nothing a/b radios

[Kcaz25]

This a question my cousin Brian posed. (He'll be watching this so if you could tell him that he should register here. ) If a receiver or transmitter says 27 mhz on, does that mean that it will only work with 27 mhz crystals? https://www.ssl-stormerhobbies.com/c...pl?pn=AIR92837 this is the receiver that I have right now in my BL xxx-t, except it says 75 mhz on the case, not just the crystal. I was going to put this crystal in it https://www.ssl-stormerhobbies.com/c...&pn=AIR9301274 . my transmitter says 75 mhz on it too, would this work? I could just get this https://www.ssl-stormerhobbies.com/c...ns&pn=JRR13575"

He's pretty smart just neither of us know much about radios. Its going in a MMM combo powered 8ight-t BTW.

Thanx,
Zack