I noticed some oil drops while my truck idled during a 900 mile recovery from Warner Robbins. 12,000 miles on an '87. Cleaned the engine and found slight seep at the front of the forward head within 100 miles. Kept an eye on it for another 500 miles and find the front edge of the block is damp, but no dripping. While the leakage isn't reflected by lower oil level, I do wonder if the gasket is being eroded or weakened and will fail catastrophically.
Lost a little oil from the bell housing too, so assume the rear main seal is flaky. I figure on watching it and procrastinating on replacement until it becomes severe.
I hope I'm on the right track.