You should use the same af90 compiler for F90 and FC, and make sure and use
single quotes around the compiler options like shown below.

The '-lU77' adds Unix compatibility library which is necessary for MPICH-1

This is for the latest version of MPICH1 1.2.7p1

wget http://www-unix.mcs.anl.gov/mpi/mpich1/downloads/mpich.tar.gz
tar -xzvf mpich.tar.gz
cd mpich-1.2.7p1

export F90='af90 -YEXT_SFX=_ -YEXT_NAMES=LCS'
export FC='af90 -YEXT_SFX=_ -YEXT_NAMES=LCS'
export FFLAGS=-lU77
./configure --prefix=/opt/mpich-1.2.7p1 --lib='-L/opt/absoft10.0/lib64 -lU77'

make
make install

Now both mpif.h and mpif90 wrapper should be installed. You can verify the installation
with the following command:

/opt/mpich-1.2.7p1/bin/mpif90 -show
ln -s /opt/mpich-1.2.7p1/include/mpif.h mpif.h
af90 -YEXT_SFX=_ -YEXT_NAMES=LCS -L/opt/mpich-1.2.7p1/lib -lmpichf90 -lmpich -L/opt/absoft10.0/
lib64 -lU77 -lpthread -lrt
rm -f mpif.h


We would recommend you update to MPICH2 if you do not need to run on a heterogeneous cluster,
as MPICH2 is still being actively developed.