It is not necessary to pull the engine to replace the intake manifold gaskets. It can be removed and replaced with the engine in the car.

Use Shoebox's cam removal and cam install procedures, there is a section specific to removing and installing the manifold.

http://shbox.com/ci/cam_removal.html

http://shbox.com/ci/cam_install.html

If you do choose to pull the engine, and there is really no reason to do that, it is easier to drop it out the bottom.