To transport a handgun in a vehicle in PA you have to possess a license/permit from ANY other state. Without a license/permit you can only transport a handgun in a vehicle to/from a very limited number of places: a range, gunsmith, vacation home, between home and place of business(you own an interest in).
Without a license/permit you absolutely cannot transport a handgun in, on, or upon a vehicle just to merely open carry somewhere. It doesn't matter where it is unloaded, or encased, or carried openly in the vehicle - the law prohibits carrying in a vehicle unless licensed(except the few exempted locations). Unregulated open carry is legal on foot and outside of Philly.
So, do you have a license or permit from any state? If the answer is no, then no you cannot. If yes, then yes.