voltage gauge potential fire???

[cataclysm80]

According to the factory wiring diagram, there is a 10 gauge wire between the starter relay and the battery.
Since the goal is to get the current from the alternator to the battery, IF you decide that you need an 8 gauge wire from the alternator to the starter relay, then you should also upgrade the wire between the starter relay and the battery to 8 gauge so that it can carry the current.


The fusible link is a special piece of wire that is smaller gauge than your regular wire.  It is designed to be the weak link in the system and melt apart if you have a problem.  This is a similar concept to a fuse popping. 
The fusible link should go between the starter relay and your new wire.
Fusible link should be available at local parts stores, and if it isn't, they should be able to order it.
For a 10 gauge wire, the chart calls for a 14 gauge fusible link.
For a 8 gauge wire, the chart calls for a 12 gauge fusible link.

Fusible link is less sensitive than standard fuses, so it's better able to withstand temporary power surges and spikes without blowing.
If you were to use a standard fuse instead of a fusible link, you'd find that the fuse popped semi-regularly during heavy electrical use.
Fusible link is an older technology that I don't think is used much on new vehicles though.  You could probably use a Maxi Fuse instead if you wanted.  Maxi Fuse is like a bigger version of a standard fuse, and it's less sensitive and slower to blow.
The question becomes what size of fuse to use.
The purpose of a fuse is to protect the wire, so a fuse is sized according to the amp carrying capacity of the circuit it's protecting.
Look at the smallest wire diameter in the protected circuit, figure the length that wire runs, then read a chart to determine what is the maximum current it supports.
Yep, it's those same charts above that don't quite agree with each other.
The idea is that the fuse rating needs to be somewhere in between the Amps being put through the wire by the alternator, and the Amps required to melt insulation off your wire.  This way the alternator doesn't blow your fuse, and your wires are protected from heavy current loads in case of a short.
Length of the wire makes a difference, so measure how long your wire will be with your chosen routing.

If your fuse is appropriately sized to protect your wire, and the fuse keeps blowing, and there's not a short somewhere, then it means your wire isn't big enough.  Try again with a bigger wire, and that will let you run a bigger fuse.
Luckily, this is a fairly simple project with a short piece of wire, so if 10 gauge doesn't work out, you can try again with 8 gauge.

[cataclysm80]

Lastly, assuming I can make this switch, as long as my grounds and wires and connections look clean, leaving the ammeter stock should "most likely" be okay?  Otherwise I can unplug it like Redline said and wind up the black and red ammeter gauge wires. 

There are little square cardstock isolators on both posts of the ammeter gauge.  They're supposed to keep the wire from contacting the gauge body (which is grounded).  At the very least, you need to make sure these are in good shape, because if the wire end wears through one, it will be a lot of heat and sparks inside your dash!
Cardstock just isn't very durable, maybe they could be replaced with nylon washers or something?

The ammeter is supposed to tell you if your charging system is charging or discharging.  Normally, the gauge runs with the needle showing a slight charge.  (just right of center)
Once the alternator bypasses the gauge, the gauge will never read a charge, and will not serve any useful purpose.
The gauge would always read on the discharge side.  I don't think this would prevent any other car features from functioning, but I'm uncertain about the long term effects of running the gauge in a constant state of discharge.  It was not intended to be operated that way, and may or may not eventually damage the gauge in some way.  Since the gauge will be unable to serve its purpose of indicating the status of the charging system, it's probably better to just unplug it as Redline suggested.