It really depends on the sort of topics you wanna work on during your doctoral studies. Political Science schools have the subject of politics as their foundation and the methodologies applied will be very different from what you would expect in econ programs. For policy schools, training would be more school-specific (at Harvard Kennedy for instance, you could receive training comparable to that of a std top 20 econ shop), but one thing for sure is that they will put a strong emphasis on policy research. Plus, from what I heard, it would be a hard sell for you on the econ market as the name Public Policy puts you at a disadvantage.
In a nutshell, if OP is good with the thought of joining a policy school or a mid- to lower-tier econ shop upon graduation, a public policy PhD is perfectly fine. Otherwise better do a std econ program and, if necessary indeed, contact the ppl whom you wanna work with outside the econ department.
Hope it helps with your question.