Penning Ionization reactions in a flowing helium afterglow are studied through measurements of the ejected electron energy distributions, P(e), and through spin angular momentum conservation measurements. Measurements of electron energy distributions from the Penning Ionization of Ar, N2O, CO2 by He(23S) metastable atoms compare quite well with known energy distributions. In addition, the Penning electron energy distribution of Rb is reported for the first time. Spin dependencies of the Penning process are studied by spin orienting the He(23S) metastable atoms prior to their collision with the reactant species. Measurements of the polarization of the electrons ejected in the Penning process provide a means of discerning the relative strengths of spin conserving and spin erasing entrance channels. The degree of spin conservation measured in the Penning Ionization of Cl2 and O2 (55% and 3%) agree qualitatively with predictions made from P(e) measurements of Cl2 and 2.