There are several YouTube videos that show various stages of disassembly/inspection/reassembly. Some are rather long so I didn’t watch them thru. You may find what your looking for. Do a search on “SM420’ and it will bring up several. Good luck!
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum