Cannot reinstall lower unit on 1990 150 blackmax

I'm hoping people of the internet can save me from this one. My buddy and I changed the water impeller on my Mercury outboard today. Once we went to reinstall the lower unit, we struggled to get everything lined up. We kept trying and got to where there was maybe an inch or two gap between the bolts and assumed the splines weren't lining up. We turned the shift shaft one notch to put it into gear and allow us to move the prop and align the splines. That got us a little bit farther, but not all the way. There is resistance to the prop, so we know something is lining up. The flywheel even turns, but there is still a half inch gap or so. We used a ratchet strap to hold the lower unit and save our backs, and if I try to force it up there with it, there is a lot of pressure and something feels wrong. We can just about start the nuts onto the bolts. We even took the water pipe off with no different outcome, so it's not that. We can take the whole unit out and retry inserting it completely evenly, turning the prop, sliding it in there but it still wont go all the way in. Any response will be greatly appreciated, please and thank you!