What is wrong with the B16 that makes you want to change it? If it's just going to be a driver, the B16 is a capable dependable engine too. Yes some bits may be getting difficult to find. I guess it depends on what you want in the end.
If your dad's intentions are to do burnouts, a stronger B18/20 is likely a better choice.

planetman's thorough comments a right on as usual.

I guess I like to keep things simple and just keep what is already there. Me? I'd evaluate how the car is intended to be used after the fix-up and then decide if an upgrade is warranted. It may be simpler to do that than the swap.
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig