just some fyi you can swap crystals in a am radio. like run yellow to yellow or red or brown you can also swap rx to tx and tx to rx and run what we called 1/2 freq .. no lose in control will occur.. just a mind blast..lol swap am radio to 2.4ghz less can happen unlike green..
no need to go with way outdated am 27mhz . just get a new 2.4 ghz way better ..I'm almost sure any am crystals will work. pick 1 of the 6 that are available.