I had a very similar
oil leak and found the intake manifold very loose when I re-torqued it. No vacuum leaks, but manifold needed tightening. Not sure that was even the leak as the valve cover was even looser and the primary source of the
oil leak. Make sure those two items are to torque limits before you start taking things apart. If you do take the distributor out, make sure you mark the position of the inside rotor. I didn't and had a little "fun" trying to find the timing to replace the distributor.