  In response to recent experimental studies we investigate Coulomb distortion
effects on $(e,e')$ reactions from medium and heavy nuclei for the case of
electrons and positrons. We extend our previously reported full DWBA treatment
of Coulomb distortions to the case of positrons for the $^{208}Pb(e,e')$
reaction in the quasielastic region for a particular nuclear model. In
addition, we use previously reported successful approaches to treating Coulomb
corrections in an approximate way to calculate the Coulomb distortion effects
for $(e,e')$ reactions for both electrons and positrons for the case of a
simple nuclear model for quasielastic knock-out of nucleons. With these results
in hand we develop a simple {\em ad-hoc} approximation for use in analyzing
experiments, and discuss methods of extracting the ``longitudinal structure
function" which enters into evaluation of the Coulomb sum rule. These
techniques are generally valid for lepton induced reactions on nuclei with
momentum transfers greater than approximately 300 $MeV/c$.
