I hear you Mike after reading all the horror stories of what residual casting sand in the engine block can do to the egr cooler which can clog and take out the oil cooler.
I want to do the same but couldn't make heads or tails of where the heater lines are near the HVAC black box on the passenger side. I emailed Dieselstop about whether their kit would fit our vans and never heard back.
I also wanted to add the vacuum-controlled valve they sell that stops all coolant flow to the heater core (like many of the automatic climate control Ford trucks have) so I don't get so much hot air on the vent setting and the AC would work more efficiently as well.
My van has the factory rear AC/heat and those heater lines are readily accessible on the inside of the frame rail. I thought of putting a filter there, but wonder if its too far away from the engine block to do much good.
Will be very curious to read if others have addressed this issue.