Post Road Trip Blues

Yeah, start reading up on instrument voltage limiters- Most plug into the circuit board, others (and I believe your Barracuda is one) are integrated into the fuel gauge. They're still serviceable, though. Replace it with an electronic limiter, they're much more reliable and have built in failsafes to protect your gauges in case of failure.
RTE is highly recommended
RTE limiter - rte (rt-eng.com)
Further down on the page they also link to a "how to" for replacing the internal limiters.

P.S.- Road trippin' with an 8 track- you're my kinda guy!