Dan,
The vaporizer you pictured first may look very familiar as it is set up the exact same as what would go on your Challenger it is just a lot bigger. On a Challenger, Pacemaker or MH 25 the throttle and water valve are cast into the Carburetor.
On the 12-20 and 20-30 Wallis the throttle and water valve are cast into the Vaporizer.
Joe