The 48 degree pushrod angle advantage should be quite evident especially since we are talking R3 blocks here and MOST don't use that block to build a 600 hp engine, also you stated stroke would be limited....which obviously to an extent but one of my engines is a 9.2" deck with a 4" stroke but is siamese bore and is it 4.165 and is roughly 434 cubic inches and makes excellent power so in my opinion a 9.2" deck is not a disadvantage in any way shape or form.