I just looked, OPGI carbs are $400, same carb through Summit Racing is $300. Ebay sells them cheaper. I don't think even the OPGI carb is new, probably rebuilt by someone else, then they add there mark up to it. If it is a real Pontiac carb, then all the linkages and vacuum ports should be there. You could just get one at Autozone, and take it back if doesn't work right. The OPGI ones aren't number matching, the rebuilt number matching ones on ebay are $750-$1000.. If it's not the right one, then it's just a Qjet..
Converting to electric choke is just getting an ignition hot wire and run it to one side of the choke, ground to the other post, easy.