Best for that setup would be the Boyesen rad valve. When I got my full specs Ed spent an hour or 2 explaining why that setup is the best. (Scientific flow calculations etc that were way over my head) One of the pros I can give is that there is a plate the carbs mount on, and that is held to the intake manifold with 4 bolts you can actually reach with it in the ski. (The carbs stay bolted to the plate, no linkage to worry about and no stubborn bolts under throttle shafts) It's also sealed with O rings, so when you pull carbs to play with jetting the manifold is super friendly.