Well if you have a K24A in your car without engineers cert and telling your insurance company then im sure it wont be insured as its not legal.

Also, you could have an agreed value on your car. Insurance price will be through the roof but you could keep it insured...

Another thing to think of... In an accident, how often do you damage the engine??
If you insured the cost of the shell you could get another one and throw the running gear in.

Regarding insurance on the track. I dont think your normal insurance would cover that. I'm not sure if you can get insurance on the track???... You are in control and at risk and you have put yourself in that risky situation. I think if your too worried about damaging your car then maybe a track isnt for you. Theres always the chance of an accident.