Description of this project.  MUST READ !!! 
It's only a few parts but installing it in an Icom IC7300 **** IS NOT EASY***  !  Read the Description and look at the photos.
You might permanently damage your radio if it isn't done carefully. I take no responsibility for this if it occurs.

Locking an IC7300 with this  interface requires ~10 dBm at 41.344 MHz, from a good external reference. Either a Bodnar GPSDO or
the  GPSDO Reference Board described elsewhere on this site can work well.