Tom Tanner has gfortran 4.4 (and gcc 4.4) packaged up at
http://n900.tannerlabs.com,
so this is what he used to make his version of R. Using this, I successfully compiled and installed R-2.12.0 along with all the recommended packages. This takes up 55 MB (including the online docs), and seems to be working fine.

Cheers, David Duffy.