Garmin 5 pin to Furuno 10 pin

[gofastsandman]

I have a Garmin 240 blue ff and 162 c gps if anyone wants them . Cheap
I found a Furuno 1610 combo.
I have an Airmar p 66 on the transom w/ the 5 pin . Furuno is 10 pin. Anyone ever pig tail this conversion?
I am told by a Marine electrician that you can do this if you cut each wire individually . He said if you cut the whole cable you`ll blow diodes and such and no more ducer.
My understanding is the Garmin has 1 shared ground pin whereas the Furuno has 5.
Thx,
GFS