No Power in the car, but there is in the engine bay

Even with removal of the ammeter in the circuit "ALL" your alternators output still goes through the bulkhead at the firewall. With a 60A alternator you should seriously upsize its output wire to an 8ga wire, and bypass the bulkhead altogether like the schematic shows but run it straight to the battery, add in a 12ga fusible link between the 8ga alt wire and the battery. If you do not so this you run an even higher risk of melting that bulkhead. The stock alt output wire is i believe only 12ga. Thats good for 20A output, barely ok for up to 30A if you decide to do the bypass, and i do recommend it before you fry your bulkhead connector especially with running a 60A alternators output thru the bulkhead, Do not buy wire thats listed as CCA wire. Its junk. Its copper clad aluminum. Cheap chinese chit. Buy marine grade AWG 8ga. You can buy from pico wiring 12ga fuse link material. I made up multiples of this 12ga fuse link to keep 1 or 2 in my glovebox.

If you want, i can post pix of my setup w the fuselink at the battery. My wiring is currently being mocked up. My "battery" is a cardboard box that fits the battery tray lol. Once its done, it will be removed so i can finish up my engine compartment and paint it.

If you decide to run that 60A and you dont bypass the bulkhead and run it straight to the battery, and then you "smoke" the bulkhead connector, well then you will have a bigger problem and a non working car once you "let the magic smoke out"