I don’t remember ever hearing of a tall deck 454 either. 366 and 427 always come to mind when thinking of tall decks. Learn something new every day!
The later Vortec 7.4L in the medium duty was an L21 while the L29 Vortec 454 was used in everything else. I don't recall the L29 being used in the medium duty and I don’t recall the L21 being a tall deck either, but I could very well be wrong as I've only seen one loose L21 ever. It was an odd engine as it had coil on plug and an electronic throttle body. It was found in RV stripped chassis and medium duty trucks. Many people confuse these engines for 8.1L’s because of the coil packs.
