Trying to start my new engine, cranks really slow and starter to flywheel mesh sounds

Awful.

Trying to start my new engine, and it is cranking really slow. On top of that the mesh between the flywheel and start sounds off, like they are too close together. Batt is showing 12.75volts, and the starter worked fine on my old setup. Difference now is I am running more compression, and a McLeod bell housing. Anybody have any experience with this?

As a side note. I am using the factory 1991 start that came in my car, 157 tooth Ford Racing flywheel. According to my instructions that came with the bell, I should leave the starter spacer in the block plate for this combo. It kind of sounds like the starter gear is jamming into the flywheel and not engaging the teeth on the flywheel.