454+Berk, Balancer pulley to transom (no mc water pump)- 51" to 51.5" no set back (as measured at valve cover height) slightly less at the bottom. ~6" less with setback.
Put that Mc454 on a diet, Ditch the water pump (its got one outback), iron intake, power steering pump (jets are true power steering- no power, no steering

) thermostat setup, iron exhaust manifolds (logs are lighter, headers are lighter yet) get aluminum 4 pt mounts. Sounds like an ambitious project.
Daniel