The restrictor fitting for my O-320 D2G is a 45 degree AN823-4 with an insert/plug that has been drilled to 0.04". It goes in a hole in the engine case right next to the engine mount. It has to be clocked just right BEFORE you mount your engine because you are going to connect a hose to it. I used Aeroquip 303 hose. I should have used a "lifetime" hose because the 303 hose has to be replaced periodically and is very hard to reach, being behind the engine mount. The time came this month to change that hose and I fiddled too much with the hose fitting and jiggled the restrictor fitting and now have a tiny oil leak from the fitting, where it is screwed into the engine case. It seems to me that every Lycoming O-320 owner has the same issue with the hard to reach fitting. Wouldn't it be great to have a low-profile fitting for the engine case that, like a banjo fitting, could be clocked in any orientation and tightened? Or be able to take off oil pressure from some other location?