I'm pretty sure the L syntax has gone away in Python3, with numbers being auto-promoted to Long if they're going to overflow. I'm a bit hazy about this, but I think I talked to the maintainer over lunch at PyCon two years ago.
There's actually no externally-visible long type at all in Python 3, it's all done transparently now. That said, I'm not using Python 3. The promoting behavior you speak of is how Python 2 works.