Directly available for powerpc-darwin in
https://sourceforge.net/projects/freepascal/files/Mac%20OS%20X/ are:
2.6.4, 3.0.0, and 3.0.2.
Version 3.0.4 has not been built. If you really need this, you have to build it from sources. I did not test it recently, but the general rule is to use the previous version as bootstrap compiler, iow. for 3.0.4 you need version 2.6.4. Version 3.0.0 and 3.0.2 may work, but no guarantee.
This is the short version of "How to build fpc with a bootstrap compiler". For more explanations see the FreePascal wiki.
The only thing needed for bootstrapping is the compiler binary, iow. the binary "ppcppc". Place the binary somewhere on the disk and cd into the source directory. The following command will build the compiler, with rtl and all packages:
make all OPT="-ap" CPU_TARGET=powerpc OS_TARGET=darwin PP=PATH_TO_YOUR_BOOTSTRAP/ppcppc
On the powerpc, this will take quite some time.
Actually, I am just clearing up two G4 PowerMacs. One 800 MHz Quicksilver and one Dual 867 MHz Mirror Drive Door. Except for the power supply of the MDD, all parts are functional. Do you need something?
MiSchi