How did you prepare the rods? If they were re-babbited did you use new shim sets and set the clearance as per the shop manual? If the rods were machined for modern inserts did you doublecheck with plastigauge?

It's not uncommon for a fresh 216 to be very tight until you start to get everything wear mated. Judging resistance at the crank is deceiving too when everything is fresh. Can the starter spin it at all?