I have a 1992 sportster 883 deluxe with a speedometer only, I would really like to install a tach. Someone locally is selling a speedometer and tachometer combo, tach diameter is smaller than speedo, from a 1991 sportster 1200. The wiring harness from the tach is there.
The question is, can I install this combo unit easily, is the wiring from the bike's harness ready to accept the tach? My bike currently has 5 indicator lights; low beam, neutral, oil, and left and right signals, the combo has only four holes; three across and one above centered. Can I simply remove the indicator cluster and mount it to the new bezel?

I have a few days to decide if I want to buy it, Any help would greatly be appreciated.