Examine your radiator cap! Does it look like its ever been Replaced ???
Bad cap, can cause overheating.
If not, I would replace it simply due to age.
If you replace the Thermostate, be carfull not to overtorque the plastic cover on the thermostate, its made of plastic and if you overtorque the two bolts that hold it on, it will not reseal.
I suggest ordering new thermo, cover, and o-rings.
Also if you do this job, its a good time to replace All the rubber hoses around the front of the Radiator.