1963 Series IIA with 2.25 petrol. I removed the three bolts holding the thermostat housing on and broke one. I looked at Rovers North to buy new ones and they are 1/4". My machinist friend looked at the old bolts and thought they looked like 6mm. Does that make sense? Are the three bolts that go through the housing into the head 1/4" or are they metric? Further, the RNC bolts are 2.5" long, but the old bolts I removed are 3" long and someone put several washers on them to shorten a bit. Thanks in advance.......