When you buy the car ask to see the latest MOT stuff (esp if there was an emmissions test). As its all computerised now it tells the mot tester if they have to do one and its hit or miss on 92 to 94 cars (my 94 panda gets away without )
I thought all injection cars registered after August 1992 have to have a 'cat' test. It doesn't matter if you have one, but the emmisions restrictions are so high, you normally need one. Carb models would keep the 3.5% CO until cat tests were made mandatory in 1994. Hence the hit and miss emissions requirements- carb and injection Pandas were optional between 92-94?
Also, what you said about the engine not changing the emmissions requirements is of course correct. I have been caught up in kit cars and SVAs for too long, where enigne age is important as the vehicle is 'newer' than the engine.
Extra space for exhaust will be handy if I want to fit the exhaust parts from the punto, so I will probably go for a really late one now.