The 2 wire plug on top is the vent solenoid. It looks identical to the mixture control solenoid on the passenger car carb. The trucks never used ECM controlled fuel mixture. The only thing you should have to do is find out how GM controlled the vent function (I would speculate that any time the key is on the vent solenoid would be energized to close it, if that's the case you could take any key on B+ and power it) Bear in mind that you should retain all the emmision crud to match the carb. You might do better with an earlier manifold and QJ.