Did the car use a proprietary chassis, engine, gearbox and running gear?
Not everything, no:
Quote from the B&B website:
HCS Racing Coupe - $25,900.00HAND LAID FIBERGLASS BODY
CUSTOM TUBE FRAME
PREWELDED MOTOR AND TRANS. MOUNTS
NARROWED 9" FORD REAREND
NEW MOSER AXLES
11" DISC REAR BRAKES
ADJUSTABLE 4 BAR TRAILING ARMS
QA1 ADJUSTABLE REAR COIL OVER SHOCKS
ADJUSTABLE TUBULAR FRONT SUSPENSION
QA1 ADJUSTABLE FRONT COIL OVER SHOCKS
WILWOOD FRONT BRAKES WITH CALIPERS
CUSTOM PEDAL ASSEMBLY MOUNTED
18 GAL. POLY URETHANE GAS TANK
STEERING INSTALLED WITH REMOVABLE HUB
COMPLETE LIGHT KIT INSTALLED
HOOD, DOORS AND TRUNK HINGED & LATCHED
WINDOW FRAMES & PLEXI GLASS WINDOWS INSTALLED
PLEXI GLASS COVERS NOT INSTALLED
ALUMINUM RADIATOR INSTALLED
PAINTED HEADERS & SIDE EXHUST NOT INSTALLED
ADJUSTABLE SWAY BARS FRONT & REAR
ADJUSTABLE PAN HARD BAR
KIRKHAM GAUGES WITH REVERSE SPEEDOMETER WITH SENDING UNITS
Unquote
It doesn't say what the engine is, so maybe it's the builder's choice?