8.1 was a useless motor really, which was why the 6.0 supplanted it, and the 6.2/L92 outclasses it. Terrible gas mileage particularly when towing, didn't make much power for its size, unique enough from both the traditional BBC and LSx to have almost no aftermarket support, and weighed a ton. If you needed the towing capability you bought the excellent duramax. Other than displacement bragging rights, there wasn't an ideal purpose for it. And an LS/LT block as is won't support 496 cubes without going with Darton MID sleeves and a tall deck, which is rather impractical for mass production.