The gauge variance of wave functionals for a gauge theory quantized in the momentum (curvature) representation is described. It is shown that a gauge transformation gives rise to a cocycle, which for theories in two space-time dimensions is related to the Kirillov-Kostant form. Various derivations are presented, including one based on geometric (pre-) quantization. The formalism is applied to two dimensional gravity models that are equivalently described by B-F gauge theories.