What do you call good Sud???
Good as in Concourse winning.... say £10 to £15K
Good as in a tidy and solid drivers car to take to shows and be proud of £6K to £10K
Good as in still a hell of a lot of fun to own and drive, £3.5K to £6K.
or it will be good when you have spent a load of money, but still enjoy it anyway... £0.5K to £3.5K.
The bad ones are the ones you end up paying too much for, unfortunately making that judgement isn't always easy. External appearances and asking prices can be deceiving.
You need to do lot's of research and see as many as you can find. Don't limit yourself to 1750's though, look at other coupe's, like the step fronts or the 2000GTV's, even if you have set your heart on a 1750, (No problem with that ), you will learn about the quality of the cars and things to look out for.
Buy yourself a copy of The buyers guide by Keith Booker