sorry- didnt read the entire 5 pages again. Did the shop do anything on the motor or just the rack?
Once the car cools down, check for obvious things first like
no coolant in the overflow
no coolant in radiator
loose hose clamps
busted hoses
cracked overflow or radiator leaking- look under the car for signs of leaking
clutch fan not working- when it is warm it should spin about 1-2 revolutions, when it is cold it should have resistance- maybe 1/2 a revolution. If you can grab it an spin it easily when the car is cold and/or you see the dark fluid leaking from the clutch assemly, or the fan blades are cracked, then time to replace
Thermostat stuck closed- the upper hose will be colder than the lower hose
Water pump- is coolant coming out of the weep hole- bearings are bad
Water pump- if you can grab the shaft and wiggle it, the pump is bad
Is the front air dam still in place
If they did do top end work, then you add to the list. They
didnt burp the air out
screwed up on the install of the heads, intake etc- could be a lot of things
Bottom line drive it as little as possible.