Tall Deck blocks have a much higher deck hieght.
You can quickly identify it at the upper waterpump bolts. On a shorty, the distance from the upper waterpump bolt to the deck of the cylinders will by ~0.200", and the tall deck is ~0.600", The difference is 0.400"
The tall motors have longer rods, which produce more torque - not noted for revs.
I don't think the 454 was ever offered in a tall deck - the 366 and the 427 were offered both ways, but I think the 454 and all later Mark IV blocks are all short deck.
I'm no expert, but back in my muscle car days I do recall researching this topic -