On a Mac Pro: uname -a Darwin computer.local 8.9.2 Darwin Kernel Version 8.9.2: Thu Feb 22 18:08:23 PST 2007; root:xnu-792.19.2~1/RELEASE_I386 i386 i386
machine i486
set | grep TYPE HOSTTYPE=powerpc MACHTYPE=powerpc-apple-darwin8.0 OSTYPE=darwin8.0
So nowhere is there any mention of x86-64. that really throws a spanner in the works for porting 64b apps.