PARALEX have TONS of unreleased stuff apart from these 3 tracks, just check out their website on the recordings page and you'll get mad
95% of everything they recorded was never issued officially, nor bootleged as far as I'm aware
I think their "Dogfight" song they recorded in 1981 is the fa-*test*-('") thing I have EVER heard from a band so earlier as 1981, perhaps with "Down the Road" from Bitches Sin. They got very close to thrash metal 2 years before Exciter, Slayer and Metallica, and this song is faster than any Venom stuff