That looks more like a number that would be stamped on the front of the block, drivers side, just below the top of the deck.
Let me say the same thing @dadsbee said, another way. Look on top of the casting on the rear of the block....the one that the bellhousing bolts to. If the VIN was stamped in 1968, that is where it will be. More to the drivers side top of that cast flange. The transmission VIN will be stamped on an automatic trans bellhousing directly below it...or side by side, like mentioned. Look at post #13 above for an example.