Isn't there a suitable port already in the manifold? If there's no flow-control valve on the heater system, you've already got your bypass.
I'm out-of-town, I don't have a SBC Vortec water pump to look at--is the hose on the Vortec pump on the inlet (suction) or the outlet (pressure) side of the impeller?
I'm out-of-town, I don't have a SBC Vortec water pump to look at--is the hose on the Vortec pump on the inlet (suction) or the outlet (pressure) side of the impeller?