Ohh. There is only one way to heaven and that is to be born again. Being Catholic does not preclude being born again. If your dad believed in the Lord Jesus Christ then he was born again.
Now typically in P vs C debated it becomes easy to start saying the other believes a different gospel and therefore the wrong one and therefore is not saved. I don't go there simply because I was a flaming athiest and amazingly ignorant back when I was 21. When I got saved, I was born again. But I was still very very ignorant. That ignorance didn't change the fact that I was saved when I believed.
Catholics know far far more about the Lord than I did when I first got saved, but I was still saved.
I think I'm rambling.