Rebuilt transmission, the moment of truth. Info?

Could park be caused by the parking pawl not being setup correctly?

Yep.
Or the park rod on the valve body linkage isn't there.
There is a tappered side on the pawl that allows the rod to push it back engaging it into the park gear, and you might have missed the opening it goes through in the case.
When the rod goes through the right opening you will feel and hear a pretty definate CLICK as it goes in, and usually have to turn the output shaft to line up the pawl with a notch on the park gear before it WILL go in.
Does either of those sound familiar?

Start with all linkage rods disconnected and move the brackets on the trans by hand.
Does anything work that way?

Also, I don't think 9 quarts is enough as the converter holds 3/4 of that or more.
If I remember right 11 is the capacity.