Installing Python on Mac 10.5.8 64-bit
It's been a long time since I had to do this for 10.5.8, but I followed these instructions:
http://web.archive.org/web/20090508090926/http://blog.captnswing.net/2009/04/19/python-mod_wsgi-64bit-mac-os-x-105/
(note that the original website is gone, hence the WayBack link)

Here's a post I made on the topic back when I was trying:
http://buffalothedestroyer.blogspot.com/2009/04/python-64-bit.html

But, do you need 64 bit python on 10.5.8?  Frankly, I don't think it's worth the pain - I'd pay a few bucks and upgrade to 10.6 or 10.7.

If it's just a problem with 32-bit python, which python are you using? (i.e., what does which python return?)