There seems to be some 64-bit support for Carbon, considering the Carbon framework is shipped as 64-bit in 10.5. I know that Carbon is basically deprecated, but IIRC, some parts of it are 64-bit. Which parts rely on Carbon?
file /System/Library/Frameworks/Carbon.framework/Carbon
/System/Library/Frameworks/Carbon.framework/Carbon: Mach-O universal binary with 4 architectures
/System/Library/Frameworks/Carbon.framework/Carbon (for architecture ppc7400): Mach-O dynamically linked shared library ppc
/System/Library/Frameworks/Carbon.framework/Carbon (for architecture ppc64): Mach-O 64-bit dynamically linked shared library ppc64
/System/Library/Frameworks/Carbon.framework/Carbon (for architecture i386): Mach-O dynamically linked shared library i386
/System/Library/Frameworks/Carbon.framework/Carbon (for architecture x86_64): Mach-O 64-bit dynamically linked shared library x86_64
.hc