If it was mine I would figure out why it is so tight. As mentioned above you should at a minimum put a starter on and connect it to a fully charged battery and see if it will turn over, first with the plugs out.
When you get to the point of installing it and decide to do it with the transmission in place make sure that your alignment shaft slides in without any resistance. You will also want to make sure that you have your engine hanging square so when you lower it in and want to slide it into the transmission you have a straight shot. Jerking and shaking will lead to damaged parts as mentioned above.