Two things come to mind. The rear corner of the intake where the water passage is blocked by the intake could be leaking. Could be running down the very back side of the block and dripping off the pan rail.
If you have a small telescoping mirror and a flash light, you should be able to take a look. Could be as simple as a re-torque on the intake to make it stop.
Second is I believe there is a freeze plug behind the starter on the side of the block. It could be dripping some too.
If you can find a radiator pumper-upper, that will make it a little easier than trying to get it hot enough to build up pressure.