This pic may be helpful. Look at the left, and down for the clamp and bolt. The bolt hole is open and will leak if not closed. Use a short bolt that won't extend into any moving parts. Some teflon tape will keep it from weeping.
http://www.trifive.com/garage/55%20Chevy%20Assembly%20Manual/6-6.gifPicture is from a later model engine but most are like this one. My 235 has another bolt to the oil pan so there might be a difference in the support clamp. If yours is secure, then just close off the hole you are not using.
