Step 1: Remove Speedometer
This is usualy held in by 2 screws at the 9 o'clock and 3 o'clock postions.
Makes sure to label all of the wires and light locations before removal.
Disconncect the speedometer cable. Pretty much like most screw-on type.
Step 2: Cover Lens
This is a bit tricky but best accomplished by using a small flat blade screwdriver. The lens cover ring holds the glass to the speedometer much like the cap of a beer bottle. If your proficient with beer then you know you can remove the cap without distorting it so that you can put it back on. I'm not sure whey anyone would want to put it back on but whatever.
Start at the screw flanges, there is a break in the ring at these two locations so you can start to pry it off here.
Step 3: Remove Mechanical Gear Box
This step could actualy be skipped if you like working in tight places but since its not that big of an effort go ahead and take it off so you can lubricate the mechanism.
Step 4: Remove Fule Guage If Needed.
Step 5: Create Mounting Plate
Once you've cut it out you can modify it to get the proper positioning of the amp guage.
Screw the amp guage to the new moutning plate and screw the plate in place where the fuel guage used to be.