As long as the gasket is the right way up, marked UP or TOP you're OK. This mismatch of hole sizes and shapes may even be deliberate to control the rate of flow. The important match is where the oil flows up from the block, through the head and into the central rocker arm mount. If this is blocked no oil gets up to lubricate the rockers. If the person who rebuilt this engine modified the holes in the gasket, it may be that coolant got routed into this oilway and that is why the neat coolant is getting into the rocker area. Check the gasket when you remove the head. Take a picture.
This picture shows the holes that feed the oil to the rockers. The black areas above and to the side are for coolant. There should be no route between them.
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