So last night we got the engine back in the 49 Lincoln and got it running good but we noticed an oil leak from the oil pressure sending unit on the back by the dizzy and manifold. It's a mechanical style with a copper line that just screws into the block by way of what appears to be a compression fitting. That fitting screws onto an adapter that looks similar to a brake bleeder screw, but it's obviously not, but looks like it.

I noticed oil coming out from where the tube goes through the fitting, is there a gasket that's supposed to be in there? Where can I find something to fix this?