four wire. You have a dedicated wire to replace it now. One is the ground, which is provided by the bracket that you bolt the alternator. And the forth is your neutral. The new 4-wire cord should come with full wiring instructions. The green wire should be the ignition(-). Changing your 4-wire cord to a 3-wire cord is similar to plugging a 3-wire 120V appliance into one of those 3-prong to 2-prong plug adapters: your appliance works but it may be unsafe to use without being properly grounded. The rem slot on your amp to the rem trigger on your deck (blue wire on most aftermarket desks) 4 wire household wiring is black, red, (hot wires) white (neutral) and bare or green (ground wire). Open up the electrical access panel on the back of the range.
This is the attachment point for the fourth green ground wire from the new range cord assembly. Some older alternators have an external regulator, and they will have a smaller bolted connection to the regulator. You say 3 wires. A red and black and white are now connected to the terminal strip. Obviously you can attempt to use it for something else, such as a hot tub, but it is NOT safe to do it! The wire should be equal in size to the size of the wire that exists around the ground terminal now.