That comment is rather pithy, but may be the most useful one of the lot. You can compile 32bit x86 executables on a x86_64 system, this should be one of the first things to try. If this works (try -O0, everything else is just asking for trouble at this stage of your project), your problem is that the interpreter will most likely assume that integers and pointers are the same size and cast freely among them. Fixing that will be ... tedious, at best.

edit: but then the code supports alpha, so it should be 64bit clean...