The STD diameter Perkins rod bearing is the equivalent of an .060" undersize stovebolt bearing- - - -2 1/4" instead of the 2 5/16" standard diameter of the stovebolt Babbit rod. A 30 under crank can be turned down another 30 and it fits the Perkins bearing.
Federal-Mogul 2015 CPA or TRW CB 560AL Standard shaft size is 2.2485-2.2490" It's necessary to drill a hole in the lower bearing shell to align with the stovebolt rod dipper. I made a fixture out of an old rod, bored to fit the bearing, with the upper end cut off so I can machine a lube groove in the Perkins bearing to align with the spit hole in the top of the rod, also.
Jerry