Engine 1974 Mustang 2.8 Water Leak Nightmare

You shoulda asked, replacing the thermostat is a mine-field. The studs will always strip out of the housing, guaranteed, and usually will snap in half too. But seriously, talking engine replacement over thermostat problems? WTH.

This is how it goes - several pieces all sandwiched together with those 3 long, skinny bolts. The front cover, gasket, water pump, gasket, timing cover, gasket, rear cover. All held together by some long M6 (x75, x90 iirc) bolts. You've got to make sure you can tighten them good & tight, or you'll leak. So if your rear cover stripped, you'll want a new one. That's Dorman part 902-1064. I don't know what you're threading 5/16 bolts into, but it's not that tiny rear cover (that's what the screws need to thread into to sandwich it all together). There are no threads in the timing cover.

To replace all the pieces, and gaskets, the water pump has to come off. Chances are the inner gasket (between water pump & timing cover) wasn't damaged. That's the only one that would require that level of disassembly. The other two (front cover to water pump, timing cover to rear cover) should be replaced when the thermostat is changed. Felpro 35092, 35093. Also you need a thermostat seal Felpro 35094.