George,
Per the block identification book that I have that is a 1966 Mercury engine. My book shows that it could be a 66 to 70 428 cubic inch engine. But they use the same codes for other Re engines in that era also. I can't find the head numbers in the limited list that I have, but they sound familiar. It says this could be a Police Interceptor, may or may not be drilled for hydraulic lifters. Look for
oil galleries.
Someone with a better book will have to help you with the rest. I looked at my 428 SCJ and it has a different head number.
Ron