I'm using stock ram's horn manifolds, they fit fine and there's no issue with steering clearance issues, my engine is also very mild, maybe 250 HP?
The shifter comes up through the stock 4-speed hole in the humped trans cover with a very small amount of trim work. I useed a large rubber shifter boot to make it water tight with a leather boot cover over it to give it a nice finished look.
http://s160.photobucket.com/user/st.../350_zpsulfogj7o.jpg.html?sort=3&o=0Mike B
