Broken blower motor bolts 66 Valiant

I think I would cut the stub off and grind it flush with the plate.
Then I would get s standard fully threaded hex head screw of the correct length . Try not to use a Chinasium screw because the "steel" is sh*t.
Grind the head down so it's only about 1/16" high.
Put it in place and weld in 3 places. (Every other hex flat)
You'll never see it because it is inside the car when installed.