True, that is where the road draft tube was mounted, same as early 283's and 265's. The oil filler tube was mounted into the front of the intake manifold next to the water neck. Every after market sbc intake manifold I've ever seen has the boss cast into the manifold and it can be machined out if that was your desire. If the engine cannot breathe the pressure will build to the point that the oil will find someplace to go, probably out the dipstick tube, been there, done that.