Well, it's worth about nothing as is ...
So, I would look it over good and quote the customer a fat repair estimate. If s/he OKs the job and it takes a whole lot of extra time, your covered. If it turns out 'not so bad' you can trim the estimate and all will be happy. If they turn the fat estimate down, that's OK too. The clock probably came from a yard sale ...
I do this all the time, just make sure there are no missing (or badly damaged) parts that will have to be made. And also, make sure it is actually going to be a big time consuming overhaul. If they 'get it running' somewhere else for 85 bucks, and you quoted $375, that's not something you want to happen!
And also (again) always ask for 50% payment up front on this kind of job, for many very good reasons
Good luck,, Willie X