This can quickly and reliably do the simple, repetitive work like changing 'print x' to 'print(x)' for Python 3. But you'll probably still need to spend a while manually debugging the code on Python 3, because not everything can easily be fixed by an automatic tool.
Is there an easy way to update an old project (https://sourceforge.net/projects/twodracing/) to work with the latest Python/Pygame? I'd like to get this 2D driving simulator to run.