The thermostat just sits there in the housing. The housing should be bolted down with two 3/8-16 bolts that are tightened to 45 ft/lbs.
torque specs on head gaskets 1988 toyota corolla 4A-F
if the leak is at the thermostat housing, make sure you installed the gasket and that is torque down to specs.(you may try some silicone,not too much)
the torque for the cam shaft are 9lbs/foot
58 lbs
70
20 lbs
The cylinder head bolt torque specs for a 1972-1979 Toyota 2TC 1600 engine is 64-68 ft lbs.
98 toyota tacoma head bolt specs
1991 toyota camry head bolts torque specs
waths the wey to torque the cylinder head
216 nm