I guess I missed the part about not run in several months...I should actually read the entire post. If it ran fine prior to the several month period and now runs different I'd suspect the points are corroded, the mechanical weights are stuck in the advance position, or the lifters have bleed down. I don't see anyway for a simple fuel pump change to cause this.
BTW my timing did change all of the sudden once...turns out I had an a$$ of a roommate. At least he didn't loosen all my lug nuts like he wanted to.