I took my Indy out the other day to test the brakes under hard breaking and got a nasty high pitched scratching type sound from the rear of the car. I have drum breaks on the rear wheels and disks on the front.
anyone got an idea what that was?

JIm

Have you jacked up the car to see?
poss back plates catching

Is the cat missing ?

Sorry

I agree that is probably the drum rubbing on the backplate. Pull the drums off and look for a witness mark. Should be simple to 'Adjust' !

If it's the drum catching the backplate it will be there all the time, it's probably just dust or rust inside the drum. Get some brake cleaner or just dust the inside and the shoes and you can check for the backplate catching at the same time.