[LS short box]

Amazing before and after engine pics. Even the hoses look good but I don't know if I would trust them.
If you keep the current engine I would pull the injectors and have them cleaned and flowed.
Have you tried turning it over with the crank pulley bolt?
Just FYI there is a company in the MPLS area called TPIS. Tuned port engines were their thing back in the day.