I'd vote for hydraulic.....this AAR recreation (no idea if the Gurney cars and the T/A's were prepped the same) was painstakingly researched during the build - notice 3 holes for master cylinders and 3 resevoirs in the tank above where the masters go (2 for brakes, 1 for clutch). The exhaust was pretty crazy on these cars, I don't think they had the room for the stock bellcrank.