Stern Drive alignment issue

[moneyhole]

I had a fellow that brought over a nice clean Alpha l unit I was going to buy today and run on my boat. Before he got here, I proceeded to remove to upper portion of the stern drive and after taking off the 6 bolts, I had to use a rubber mallet 6-8 times on the upper most top portion (eye hook) to get my old unit out. All looked well in there as the in-line 6 was installed in late '08. When the guy got here and we tried to fit his complete outdrive, we could not get the splines to line up. Actually never got his lower unit to "seat" into position - the bolts only went maybe 1/4" through the sterndrive holes. As I read into the manual some, I'm thinking my engine may be slightly to high mounted in the rear.
Shouldn't the unit slide in & out with relative ease. Am I doing something wrong. We fought slidinging it back & forth for 2 hours, then I had to take a break....man my back just gave out. Tried sliding my old unit back in and it did the same thing...it's hitting or binding slightly on the top housing of the driveshaft.
I can't see how in the world you can get wrenches in there to adjust the aft ( front) motor mount.
I give ????? I don't know what to do. Nothing has gone smooth since I got this boat- it has a cheap price tag on it right now!!!!

p.s.- it ran with the old unit on - would shift fine, that's when I found out the water pump was bad and then discovered the JB Weld...... That's when I knew I was a sucker.......