Ben
That seems really odd. Do you have the original mast? If so, then the shrouds could not possibly be too long unless the previous owner never sailed the boat. Have you stepped the mast?
Can you take pictures and post? I think you will get better advice if we can see what your issues are. Unless you don't have the original mast and then ... yeah...
BTW: I have a mast and all of the standing rigging from a Macgregor 21. A friend parted this boat out and stored it in my yard. Then moved away and left me with bits and pieces. You are kind of far way to take a look but I might be able to help you out once you get measurements and if the parts fit.
Good luck,
r