It's an older unit that was converted by Larry in FL with a water box below where the carb sits. Hot water is run using 1/2" hose from a plug in the t-stat housing to the box underneath manifold and then on to a T in the top heater box water line.
1968 Camaro - 250 (No, I'm not gonna drop a 350 in it!....Jeez!) 1968 C-10 with 2 extra cylinders