i have a 54 reg 182, i just checked for obvious signs or wear on the car, asked for reciepts from services, tires, mot' and what have you.
the only prob i had with mine was the oxygen sensor, it didnt work properly so needed replacing.
I'd personally only look at a car that had the following....
4 good quality matching (at least Axel matching) tyres,
FSH, including a cam/aux belt within the last 20k.
Standard suspension set up.
Brakes have plenty of meat on them.
All that work alone will cost £1000 should you buy one that needs it.
If all those are ok, then chances are its been well looked after and will serve you well.