1983 mercury 70 outboard lower unit won't drop out

So I am trying to replace my water pump and I can't get the lower unit free it drops about a quarter inch and I have the two nuts free and the trim tab removed with the nut under it and also the nut behind it I also have the shift linkage pin popped out I tried wedges but no success does anyone have any ideas to get the lower unit to drop out

The shift shaft is splined, there is nothing to undo there.

I know it is splined but there is a roll pin that holds the shifter shaft onto the linkage so I popped it out but I still can't get the lower end to drop out

I've had similar problems with a number of different motors, especially the early ones. It's called corrosion. The splines on the drive shaft corrode into the crankshaft. They can be a real ba.sta.d of a thing to get out. Brute force generally. If the leg is dropping 1/4 inch, you've got all the bolts. You say you've undone the shift rod. Not unusual for a leg to move up and down as you describing, drive shaft stays stuck in the crank particularly on an old motor that's done a lot of work. I've seen mechanics actually cut a hole in the side of the leg at the top to get oxy/act heat on that area to try and free them. That though is the extreme but when all else fails???