I had a 1975 GP 433-G with a Tillotson from a Ski-doo TNT on it and it ran like hell. I recently found a better GP 433 G now that has it's original carb on it. I don't think I would use that thing if my life depended on it. Some of those reed valve engines will have blocks that allow dual carbs to be mounted. The 1974 Yamaha GP's, Sno-jet SST's and 75' SST's all have those. The 75' and up Yamahas, 76+ Sno-jets all have solid 2 into 1 manifolds so you have to find the older reed manifolds or do some fancy machining to run 2 carbs on them. That looks to me like it is a 1974 or 1975 carry-over GP 433-F. The gas tanks on the older ones are behind the seats and they have bogey suspensions.