GZ_Tanis: I have no idea at all if it will work. I've never written any php3 code in my life, I started learning it when they just released php 4.0.4; I never bothered to go back since I run my vBulletin on a php 4.1.2
All I can say is try it out but make good, solid, _verified_ (that they work) backups first. You may have to adjust the code though, but I don't know if I can help you with that....