Nothing is apparently easy with Smith gages. Instead of a standard compression sleeve tapered on both ends, the line fitting used a sleeve with a tapered shoulder on the gage end but had a flat shoulder towards the engine - fat chance of finding anything like that down at the local FLAPS (or Graingers for that matter). I bought a new coupling nut to fit the new compression sleeve and I'll see how that works. It may not be completely compatible with the fitting on the back of the gage, in which case I will have to look at changing it out also.
Just in case anyone else runs into a leaking Smiths
oil pressure gage.