SCCA Formula B was booming in 1968 and Brabham's US dealer Fred Opert imported up to 16 of the latest Brabham BT21C model. The BT21C was an update to the 1967 BT21A and visually almost identical.
1967 Brabham BT21C - Motorsports Market
1967 Brabham BT21 technical and mechanical specifications
1967 Brabham BT21C - Motorsports Market
Brabham BT21C car-by-car histories
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Historic Hot Laps: On-Board a 1968 Brabham BT21C - Historic Sports
Brabham BT21 - Wikipedia
available for download on the website - Historic Sports and Racing
Brabham BT21C car-by-car histories
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Ex Frank Williams 1967 Brabham Bt-21
RBE: By The Numbers…
Brabham bt21