Compiling and linking 64bit code
 

I have a question for anybody that is actually compiling 64bit programs (numerical stuff).
Is it sufficient to recompile gcc and glibc on a 64bit machine so that one can write programs that link to, say the C maths library, to make use of the extra decimal precision etc.?

I would like to build my own 64bit pkgs until alternative 64bit pkgs get added to Slack. They will eventually be used on a cluster and I don't want to install one of the Mandrake or SuSE 64bit distros if I can use Slack and just recompile two packages.