I have a Toyota forklift 55A alternator on the RR along with a CSR electric waterpump (POS), an electric fuel pump, dual electric fans from a Dodge intrepid, and a MSD 6AL and HVC coil. Purchase an amp clamp and measure the current at the alternator (big wire) with the alternator full-fielded, then measure the current on the power or ground leads to each component and add them up. My load was nearly 50 amps, and over 55A with lights on. Alternator was producing a maximum of 58A. Even if the load was under 55A the alternator would be at or near full-field just to keep up. At full-field it's just a matter of time before the alternator overheats. Want a real diagnosis instead of a lot of guesses? Get the amp-clamp and measure the alternator output and then measure all the loads and do the math. I suspect you'll find you need a higher capacity alternator or fewer electrical loads.

If you think it's the wiring or grounding then do voltage drop testing. First battery positive to alternator power lead, then battery negative to alternator case, with the the loads turned on (duh). Anything over .5V (half a volt) on any one lead and it's too much especially for new wiring. Next voltage drop from alternator power output to positive lead into each load (fan, fuel pump, waterpump etc) at the load, then alternator case to ground lead to each individual load. Again, anything greater half a volt is too much and requires a wiring repair.

FWIW, my 55A alternator is too small...and for sale just like the fuel pump and waterpump.