First it is important to recall that dipole-dipole energies are not the only cause of steric interactions. Therefore, the substitutions will affect other molecular properties associated with the steric effects such as quadrupole moments (aromaticity).
Now, if you want to address the effect these substitutions have on the dipole moment, it might be easily determined from any QM software like e.g. GAMESS, since dipole moment is one of the default properties computed.