**** me running. I just realized. The rear main. I forgot it. Sob. Guess it’s all coming back out now. :BangHead::BangHead::BangHead::BangHead::BangHead:
If you just forgot the bearing shells, just remove the rear main cap, rotate the bearing shell into the block starting on the anchor slot side and rotate the bearing into the block until the anchor slot seats in it's notch... I've walked bearing shells into the block like that without removing the crank....
See if you can do it without loosening the other mains first, and if it hangs up loosen up one at a time until you can get it to spin into position...