Your 2015 Vista's V-10 pulsing issue that started after mountain passes in Montana is likely caused by a failing mass airflow sensor, throttle position sensor, or fuel delivery problem. The "Fault received from External Node" code suggests a communication issue between engine management and instrument cluster that may be related.
Your 1989 Ford Tioga's 460 EFI system is experiencing classic symptoms of fuel pressure loss, likely due to a failing fuel pump or clogged pickup screen in the tank. The dead battery jump may have damaged the fuel pump relay circuit.
4R100 has no factory gauge sender. Add sender in pan or cooler line for aftermarket gauge. ScanGauge reads PCM temp without hardware.
To fix parasitic power draw through your 2006 Damon Challenger's instrument cluster, use a multimeter to isolate the circuit, check common culprits like clock memory and sensor wiring, and find alternative wiring diagrams through Freightliner chassis documentation or aftermarket sources.