Captain232, it may be crude, but it sure does make the point.

crashergs, if you don't have the rudder mounted yet, stand it on its tail end and get somebody to hold it steady while vertical. Place the engine & mount on the firewall. Slide the cowl over the engine and move the engine around till the prop shaft is centered in the cowl opening. Now slide the cowl off and make some marks so you can drill the holes you need in the firewall.

Ed M.