I am getting ready to install a '58 235 eng in a '52 truck. I started putting all the oil galley plugs in without any problems until I looked at the lower left galley on the rear of the block. It's the one that runs straight thru front to rear. It has two separate threaded sizes, 3/8" at the surface & 1/4" in a little deeper. Do I leave the 1/4" open & plug the 3/8" only? It looks like the 1/4" hole would block off an oil passage if I plugged it. I wasn't the one to take it apart (3 years ago) so I don't know for sure. Thanks in advance for the help.