There may be another issue other than the carb/fuel delivery. There are a number of things that can cause engine stumble or random engine shut downs (not specific to these trucks/engines - just treat it as normal fault diagnosis...) Stick to the basics first - engine tune, vacuum leaks, blocked EGR, carb function (auto choke, fuel bowl vent, accelerator pump *which looks like a possible fault etc) fuel filter/hoses/pump then look at things like distributor advance function, ignition coil. If you plan on doing the Weber install, there is a specific kit for automatic trans optioned trucks (there is an additional linkage for the transmission kick-down cable) My money is on something minor that is nerfing your engine like poor engine tune or a tired coil, lazy fuel pump or a clogged filter.