How difficult should it be to turn over by hand??

Check your rod caps and make sure they are aligned correctly. The numbers stamped should be on the same side, and the oilers pointing in. I had 3 and 8 swapped (light stampings) and it took a breaker bar to turn..WTF? 5 months later I went at it again and found my mistake. turns by 3/8 ratchet now. Still stiff but crankeable with a starter no prob. you got the cylinders oiled down and Assembly lube in the bearings? Oh yeah, if you went with an aftermarket crank, your OEM bearings might need clearancing for the new crank fillets.