Creating universal binary(ppc/i386) with XCode 3.1.2

I've been struggling to create a universal binary with XCode 3.1.2 on a specific rather large project but failed. All of my libraries included in the project are for two architectures ppc and i386. Whenever i build the project and use file on it i get:

myproject (for architecture i386): Mach-O executable i386
myproject (for architecture ppc7400): Mach-O executable ppc

Notice there is ppc7400 not ppc. This won't work on Mac os X Tiger for example and support for that os is a must for me.

Looking at project properties i can read this:

Architectures: Standard (32-bit Universal)
Base SDK : Mac OS X 10.4

I compiled other libraries(i did not do the setup for them, it was already done) on the same mac for architectures: ppc and i386. I'm wondering what am i missing that a receive ppc7400 and not ppc.