You've got it wrong, Bitcoin SV isn't a fork of bitcoin but it's a fork of Bitcoin Cash ABC also known as BCH.
For posterity's sake, I figured I'd checking and post the resolution.
First, since BSV is a fork of BCH, which was a fork of BTC, BTC addresses/keys are indeed valid in the BSV blockchain if they were generated prior to the BCH fork.
After much trial and error with multiple clients, the simplest way I found to get the forked coins was to import the compressed WIF key from the original BTC wallet into AtomicWallet v1.39.1 (which still supports importing keys). I had originally attempted to import the uncompressed keys, but Atomic always reported that there wasn't enough to cover network fees, so I just assumed it wouldn't work. When I later tried the compressed key, the coins showed up right away.
I ended up exchanging the BSV for BTC in Atomic. It was probably not the best exchange rate, but based on the going BSV rate, I wasn't going to go through any additional goat rope for a few pennies.
There are other ways of doing it, but all of them were more involved. As a guy that's been into Bitcoin as long as I have, I'm sure there are thousands upon thousands of BCH and BSV coins that will be forever unclaimed.
