On the previous 2 rods that I built using small block chev engines, I bought aftermarket thermostatically controlled fan switches to run my electric fan. They screwed into one of the ports in the center head near the water neck, and when the engine temp got up to 180 degrees they would pull in a relay to power up the fan. They worked great, but cost over $100 to buy. Now I see it mentioned on this forum that people are using fan switches that came stock on Chrysler mini-vans or something for a ridiculously low price to do this same function. Anybody out there got the true story on this?---have you done it----do you have part numbers----pictures????? I don't want to spend a fortune if I can avoid it, but I don't want to cook my engine either.