I have had my engine rebuilt three yrs ago and I have a small leak that shows on the protector cap between the engine and trans. No one can seem to find the cause. Any ideas would be greatly appreciated. It is engine oil for sure.
FWIW this forum focuses on '93-'96 last gen B- and D- bodies. But yours is my fave '60's model, so I'll offer that the rather usual suspects are a leaky oil sender, leaky intake manifold or leaky rear main seal.
Is the leak recent, or have you had it since the rebuild? Recent, look for an oil press. sender leak or intake leak. If old, look @ RMS, or perhaps an oil gallery or cam plug leaking @ the back of the engine.