Porting a slant six head

Looks like they did a nice deep 60 degree bowl cut. Now you need to "blend" the bowls, and narrow the guide bosses. You want a pretty smooth surface on the walls, and a nice smooth radius on the short side. A flame tip carbide burr followed by 80 grit tootsie rolls should do the trick. The long style burrs work the best. Put a couple layers of heat shrink tube on the shaft of the burr so you don't nick the valve seats.