Power for some key electrical components run through the OVP, so I'm sure it's needed to start the car. Chances are if it's fried internally, the car definitely will not start. If the fuse didn't blow, there was no voltage spike. So it sounds just like a normal OVP failure.
The pins have to be the same on the OVP's for them to swap over. If it does have double fuses, there's a chance it's different, but not sure. The double fused relays should have the same amperage fuses in them, though. At least they did from the factory.
