Wondering the reason for your question....Not sure just how to respond to this question. OMC made the 65 3 cyl engine up thru the 1973 model year. Their parts lists show only one head was used on the engine from the factory. Most of the 3 cyl engines made a this time frame ran higher compression head than the late 80's models-when the fuel started to go to low-lead and no-lead. OMC did not make "low compression" heads that I know of. When they wanted to lower compression, due to the fuels-they would sell a low compression "kit" which was basically thicker head gaskets. Those were sold mostly into the V6 engine lines around the 1989 time frame. I don't think they ever made this low compression kit for a 3 cyl engine. If they ever did in the late 80's it would probably have been for the larger (later model) 56 cubic inch 3 cyls engines. Your engine is a 49 cubic inch block, so later head and head gasket probably would not fit.
