The last 406 sbc I built, I drilled and tapped coolant holes in the block between the center cylinders, coming off drilled and tapped holes in the water pump, and tapped the intake for lines from the back of the intake to the drilled and tapped thermostat housing. it worked out very well. I started to do it on my 440/505, but decided not to, because of space problem w/ my set up.
