The SST-60 is a Bridgeport motor with the angled upper lip on the exhaust ports. The port timing on the SST-60 is different then the stock 70 hp. The SST-60 also uses 1 1/2" bore carbs without the black plastic tops. The flywheels on the 49.7 cid newer motors and the 70 hp 56.1 cid are the same as the SST-60. The tuner on the SST-60 is shorter and much different then the stock 70 hp. Also, although the same head, the pocket depth is less on the SST-60. You can cut the head to accomplish the same thing. Reeds on the SST60 are plastic Boyesen reeds, but use the stock reed blocks as in the 70 hp.

Hope that helps.