Not my first choice but a 389 with an MX has 16” between the firewall and the head. Other than the idiotic rear geartrain. Which one would you rather work on?
Local shop has a Mack with Leiffi’s amazing Volvo engine with the state of the art rear gears. Nut came off idler gear and destroyed the air compressor gear. If this was a normal engine it wouldn’t be a big deal. But with rear gear the transmission had to come out and you get to work under the truck.