If you get it to rotate, and you have the pan off, consider getting rid of those two bolts that install into the timing cover from the oil pan side by tapping the two holes in the cap and drilling out the two threaded holes on the timing cover and installing bolts from the balanced side of the cover. Also, since you have it apart this far, drill and tap the crank snout for a bolt and get an harmonic balancer install tool.
https://sdparts.com/i-24132641-proform-66515-harmonic-balancer-installation-tool-fits-small-and-big-block-chevy-crankshafts.html?msclkid=a79bfb1c7a11158e0918a66dbc3eb3af&utm_source=bing&utm_medium=cpc&utm_campaign=PLAs%20-%20%2425%20-%20%2450&utm_term=4582695748898622&utm_content=Brand
https://mrhotrod6.myshopify.com/pro...-tap-fixture-tool-kit?variant=1142530609
