gmp-4.2.1 has been released, and both FC-5 and FC-devel ships gmp-4.1.4. It blocks bug #166450.
gmp-4.2.1 has been out for a while, and it's still not present in either fc5 or development. If there is a strong reason not to update to gmp-4.2.1, could you please ship a gmp without mpfr (compiled with --disable-mpfr), as well as mpfr-2.2.0 in a separate package (complete with shared libs). Compiling gcc-gfortran-4.2 requires these versions so you'll need to do it at some point...
It should be noted that GCC 4.3.0 and later will require GMP >= 4.2.0 and MPFR >= 2.2.0 to build (and not only the Fortran front-end, like gcc-4.2, but also the C front-end): see http://gcc.gnu.org/ml/gcc/2006-10/msg00284.html for details
Current gmp in development and FC6 are now built with mpfr-2.2.0, though gmp itself is still at 4.1.4
*** This bug has been marked as a duplicate of 211762 ***