basic engine is the same apart from the s1 cam and valves are better, ancillary wise water pumps have different outlets so u will need to swap the pump over , s1 inlet manifold is a 2 peice job not one piece like the s2 so basicly just use the bare engine with all your s2 ancillarys and you will have no probs

flywheel and clutch are bigger on the s2 so use those