A slight issue with my '66 coupe 289 is a small oil leak at the back of the engine. After I shut the engine off, it will drip a small puddle about the size of my hand onto the ground. It does not leak while the engine is running, only for a couple of minutes after I shut the engine off. The back of the heads and intake manifold are dry so it's not leaking up there. The dripping is coming down by the bell housing cover. My first guess was a rear main seal but the fact that it doesn't leak while it's running, only after being shut off, makes me wonder otherwise.