The reverbs used a spring/transducer unit from Hammond Organ. And yes it would TWANG if U hit a bump and radio ON but not tuned to a station...
Most of the aftermarket units were sold under the Motorola brand, don't know about the Mopar version most likely built by Motorola... Back in 66 the retail price of the Motorola including (1) 6x9 speaker was $29.95..

Just my $0.02... wink