Jason, thanks for purchasing a set of those adapters. Most people with electric pumps aren't using the heater, so I didn't make any provisions for that with my adapters. However, I think there's an easy solution. The heater core normally gets water from the pressure side of the water pump, and then returns it to the intake manifold just before the thermostat. To get to the pressure side of the pump, you could drill a hole in one of the water pump adapters, tap it for a 3/8" pipe thread, and then just put in a fitting for the heater hose. This should give you the same routing as the factory heater core setup.
Good luck on the installation - Jay