Macman,
With no rope seal in place and only the crank in place, side trust correct and mains tightened to the specs, You should turn the crank freely with no big effort, with your hand only, no tools required. If You want a cheapo way to be sure it's not too loose, make a small piece of newspaper paper measuring 1/2 X 3/4, remove any of the main caps, place it over the crank, tight the main again and it should be locked or at least hard to turn. By no means it should turn free. The rear main seal rope type should place some 35-50 foot pound of drag, You can measure it placing a torque wrench in the crank snout and measuring it. As normally L6 have no bolt in the crank snout You can use a large socket driving it using the pulley key. Do it softly not to damage anything. Neoprene seals puts no considerable drag there, after the crank is tightened with one in place You can turn it the same way using hands only.
