Question: Which Formula One car besides the Tyrrell P34 was one of the most radical entries ever to succeed in F1 competition, that used flat panel heat exchangers? 
Sentence (from "Brabham BT46"): The cars, however, powered by a flat-12 Alfa Romeo engine, raced competitively with modified nose-mounted radiators for most of the year, driven by Niki Lauda and John Watson, winning one race in this form and scoring sufficient points for the team to finish third in the constructors championship.
Relevant evidence: No