Another option is to use a standard crystal/oscillator on one and let this Atmega source the clock to the other AtMega's. This requires setting the CKOUT fuse on the "master" and program appropriate full swing fuses on the other AtMega's.
Another option is to use a standard crystal/oscillator on one and let this Atmega source the clock to the other AtMega's. This requires setting the CKOUT fuse on the "master" and program appropriate full swing fuses on the other AtMega's.