I need some help/advice on fixing an oil leak that appears to be coming from the mainfold or cylinder head.

The entire left rear of the block is wet with oil - not fuel. It starts just under the intake/exhaust manifolds and runs down the block.

My first thought was to change the head gasket, but I'd like to see if anyone had any ideas or had seen this before. Compression is even across all cylinders and I'm not burning an excessive amount of oil.

Anyone seen this before or have any ideas or guidance? Thanks!