There are two trick plugs in Mopar SB
One is the one mentioned above. This is a screw in plug behind a second screw in plug in the rear of the block. You can see it looking down the dist. hole. One guy on here actually installed it through the dist. hole
The SECOND is a drive in plug which is installed before the rear main cap is installed. This goes up in the vertical gallery going up to the oil sender. There is a way that you can remove the oil sender and stick a rod down in and measure to determine if it is there
THIS WOULD NOT prove there is not a hole in the plug from say, rust or hot tanking.
This is a photo of the one in the dist. hole. The wrench is coming through a plug in the rear wall of the engine
http://image.moparmusclemagazine.co...mouth_valiant+installing_oil_galley_plugs.jpg
For some reason I can't find the dope on the one in the vertical galley, maybe someone will find it