Been filling with distilled water. Was able to get about 3 1/3 gallons filling from radiator. Will try thermostat fill then hole trick.
BTW it's a 190 or 195 degree if that matters. I have a known good 180 degree from my LA.
Need to get 50/50 Anti-Freeze and your Distilled water mix to keep the water jacket and cooling system parts from instantly Rusting with only distilled water in there.
The anti-freeze is what keeps it from rusting everything. Not to mention it won't freeze if it dips below 32°F.
360s normally run a little hotter that the 318s. I personally would run the 180° stat.