Probably the best visual, fool-proof method is that first picture. That was something of the "birth certificate", as it noted undersize this or that and also had the engine size stamped on it, as I recall. This was before they started stamping the VIN on the blocks. That information, symbols and such, was supposed to help an engine rebuilder know what they had, most possibly while the car was in warranty, in order to order parts. That was all explained in the MOTOR Manual I have for 1966 and also should be in the factory Chrysler service manual.
Other than that . . . as mentioned above, you can ask for a measurement between the two front intake manifold bolts. Unfortunately, the cosmetics on the B/RB engines were very similar, through the years. There would be model year differences as to whether the pcv was in a "can" or plugged into a rubber grommet, or the old draft tube was attached. Emissions-related things like heat stoves on the exhaust manifolds (or lack thereof), air cleaner snorkel-end shapes and styles.
If you're going to be chasing date-coded blocks and such, have to check the casting number and date codes.
CBODY67
