Sorry for the delay in the reply!
Unfortunately, old versions aren't easily available for download. If you feel adventurous, you can try to
1. make a backup of your save
2. verify that the backup works
3. double-check that you have the backup
4. then just try loading the save with the latest version, even if it isn't guaranteed to be downwards compatible with 3.71 save, if you are lucky it might just work.
If it doesn't work, or if you don't feel like trying, send an e-mail to erkka [at] enormouselk.com and I can help you get it sorted out.
- Erkka from Enormous Elk