I figured it out! The actual solution. Thank you everyone for your help. I wonder if this is the same reason so many other people have been in the same predicament, prying like their life depended on it lol. I would have made it to work with force too. I could already get within 1/4 inch from prying and ratchet straps. One more prybar and one more jack would have done the trick.
Turns out I completely forgot about the old emissions brackets that were there for the EGR hoses. They are little plates that go on between the clamshell and the block. I had totally written them off and forgotten about them when i pulled my old engine because they were emissions stuff and I threw them in the corner lol.
Luckily
@Vbb199 helped me remember
Let me know if you think this theory is correct. Seems like in the late 70's when they first started putting out EGR systems, they needed a plate there as a mount for the hoses. So they must have made a slightly shorter clamshell for these years. We know the mounts on the frame are in the same spot and they didnt rework the whole frame.
So it has to be that they made shorter clamshells for these early emissions vehicles. I cant believe how much Google searching I did and I didnt find a single post about those damn EGR plates... Can we sticky this if everyone agrees?