I haven't done the valve & compression retest yet.
The coolant is not leaking, no puddles.
Now I'm worried that the radiator is dying.
Hmmm...since, in order to run further diagnoses on the power loss, you've got to safely run the engine up to operating temp with overheating and causing further problems, I would first:
1) install a new thermostat (maybe get the 180*F Toyota thermostat along with a new gasket and new o-ring that sits on top of the thermostat)
and if that doesn't solve the problem, since you are in Texas (gotta keep cool...) and depending on how old that radiator is or if it is old and condition unknown
2) get a new radiator with hoses
On the thermostat, I'd go to Toyota (either a local Toyota dealership or
@beno if you want a MUD discount and excellent service).
On the radiator, I can't remember which one I installed last summer, but I think it was a CSF (maybe
@Spike Strip will chime in here, if I remember correctly he did a pretty thorough analysis of which after market radiator is well suited). And if you do the radiator, might consider replacing all the heater hoses too, if they are the original 30 yr old hoses...
Remember, after you break a line in the cooling system and introduce air into the system, you've got to burp afterwards, otherwise that trapped air can act as a blockage and prevent flow...causing problems (localized spike in temperature that can blow through a head gasket, for example).
EDIT: Thoughts on how to decide whether or not you need a new radiator...
1) Based on information you have about the age of the radiator/hoses/etc. (service records from previous owner?)
2) Based on diagnosis (behavior, process of elimination)
3) Based on a test (remove radiator and take it to a shop...to get tested...)
If it were me, and I knew that the radiator and hoses were the original (or by looking at it had a pretty good indication that this was so...), then I would get a new one and replace the hoses/clamps...simply because I think keeping these 2F engines cool is the humane thing to do. Replacing the hoses (including heater hoses) all at once make strategic sense, because if you replace them as they 'blow', not only do you have to deal with the headache of servicing a vehicle on the side of the road, but as you replace an old one with a new one, now another old one becomes the weak point of the system, only to blow a couple weeks down the road and you get to repeat the unhappy (and stressful) process of 'survival mechanics'.
Especially in TX, where it is hot (or so I have heard), having a trustworthy cooling system is the most advantageous position to be in.
And, based on your story above (number 2...diagnosis..), I would assume that if everything else in the cooling system is working correctly (water pump and thermostat and no blockage), then your radiator is causing the overheating.
As far as number 3, I wouldn't even bother if you have a aged radiator/hoses.
Why spend the time/money to get the one you have in there tested/'fixed'...go straight to new based on information from number 1 and observation from number 2.
Info on 'Rodding Out' a radiator:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2462475
Also, I would seriously consider getting a new water pump and gasket and installing it if you have the radiator out. Keep the old water pump (along with another new gasket) in the vehicle in for emergency...as long as the old water pump is still functioning correctly.
That is what I would do, but it is only an opinion based on limited specific information about your rig...only assuming that the radiator, thermostat, water pump and hoses are all over 10 years old, if not the originals....
EDIT: EDIT: What you could do, though, is:
1) Do the thermostat fix (see below)
2) take the rig in as is (with current radiator/waterpump/hoses/etc.) and get the whole system flushed. Take it a mechanic you trust that has a machine that hooks up to the upper and lower radiator hose and pumps fluid/cleaners/etc through the system...it cleans out any deposits (due to reduction reactions between the metal and ions in solution)
3) evaluate if you want to do the radiator/hoses/water pump fix...