Hey all. I'll start a build thread soon, but i'm far enough along I have a few questions for the group. I removed the rear heater to the box. I'm looking to tie the lines in with a heat exchanger to my espar. Espar will be on a separate loop. The line comes out of the drivers side head and returns along with the heater core loop to the top of the water pump. My main question is about a pump for block heating. Any ideas? I'd like the pump to be "flow through", so when driving I can use the van water pump to circulate coolant to the heat exchanger. Has to be one of you that has done this and found a pump that works. I have a 2000 E450 with 7.3.