at the very least it will need to be torn down and inspected. rings don't like to sit in one position for long periods, they loose there spring and tend to stick to the piston grooves, also tend to mark the wall where they are in contact.
when you refer to the side oiler passages not drilled, if you mean in the rear of the block you may have a marine block. they will
oil like a regular FE, and will not be drilled in the rear, also on the side the raised portion where the
oil galley extends down the side of the block will have a radiused machining through it such that drilling of the passages will be impossible.
so a tear down, all components checked, and go from there......there really isn't a canned plan of attack. it will all depend on what you find....