The Topper 158 30-30 that I traded back to Tallyho, wouldn't even come close to fitting any of my 25 SB2 frames, the underlug was about .100" longer than a Handi underlug. But others have reported using 158 barrels on modern frames, so it's probably just a matter of having one that fits!! The 30-30 158 barrel was a very thin contour, pretty straight from just ahead of the chamber swell, just as the superlight barrels are, about .590" at the muzzle, IIRC.
Tim