even ur car is thrashed real good right? so whats the problem?
1. knock on the various parts of the body, check if there's any "un-metal" sound(indication of cemented bodypart). also check the gap between bodyparts whether they match or not(indicates post-accident repair). i.e between headlamp and fender.
2. test drive the car on highway around 120kmh. at this speed, most irregularities (any weird vibrations, sounds, etc etc) can be noticed.
3. check if there's any leak at bottom of engine. if it's too squeaky clean, maybe already engine wash. engine oil leaks are pain in the ass to pinpoint. also check service history. which workshop? go and find out more from the car's mechanic.
4. having a problematic engine is easier than having a problematic chassis. engine problem, worst case scenario, just buy another halfcut. if body problem, i cant imagine the worst case scenario... so make sure the car ur buying has a tip top chassis.