If you have an electric fan, and an intercooler in front of your radiator, you do not need a thermostat. If the fan isn't on, you're only losing a small amount of heat though actual radiation. We've been running reverse flow for a few years, and the car doesn't take any longer to heat up.
All of the pressure in a cooling system is caused by heat expansion. The design of every TD water pump(and most likely any W/P) make it impossible to create positive pressure. All the W/P is for , is to push the coolant through everything.
The #4 coolant mod is obsolete if you reverse flow.
You don't need to be able to machine aluminum, just be able to weld it. Our first block bung was a scrapyard elbow welded to a piece of aluminum plate, surfaced with a file and a belt sander.