Ok, from all I have read, the oem amp gage is good for 50 amps. If your alternator never has a load exceeding 50 amps --no problem.
You can leave the one wire from the alternator to the battery -- this takes care of a load exceeding 50 amps. Also run a 12 ga wire from the alternator battery lug to the neg side of the amp gage -- I fused this 40 but you may want 50 -- this circuit will also go to the key ON for everything running afterward with key on plus anything running on battery like headlights would be on this same side. From the other positive side of the amp gage it runs back to the starter 12 volt lug or back to the battery -- I fused this 40 also. The amp gage will still sense discharge and charge. It works... I run a 63 amp one wire alternator.
You may want to trace out your existing oem wiring to see what is already there and what is missing.
Go down to the Gauge System Section.
http://devestechnet.com/Home/Native12VUpgrade
