Identifying cracked heads is done at a machine shop with dye penetrant testing, mag particle testing, vacuum testing, or maybe even ultrasonic testing (not common though).oh yeah thats right. those did not to appear to have any cracks anywhere none uner the valve seats none on the face. both were alright
In your case, you don't know why it was/is running red hot. A visual look at the heads is not sufficient to rule out cracked heads.
You really don't even know if you have an engine that is worth further expense/effort or not.
If the coolant temperature is accurate and it actually has been "red hot" and you don't have good compression - then time to move on ....... IMO anyway. This engine seems to have gone through quite a bit of abuse.