gcc32 -o foo ... -lg2c fails since compat-gcc-32 doesn't provide libg2c.so I am not sure what is the best solution here (sadly forcing the users to get their act together and moving to something recent isn't an option), providing compat-g77-32 with the full(?) g77 stack is one option and the other is to use the existing /usr/lib/libg2c.so.0 assuming libg2c hasn't changed at all. The users are only interested in linking from gcc-32 with libg2c and not a g77-32 so compat-libf2c is probably an option.
So compile C code with gcc32, Fortran code with g77 and link using gcc or g77 rather than gcc32. Adding g77 compatibility stuff is an overkill.