Your KTM forks could work - they are really overkill and the biggest issue I expect you might have is that they will be a bit long and large in diameter (which might limit turning radius). They are certainly strong enough though. all current trials bikes use fairly skinny conventional forks to maximize turning radius. If you use the KTM forks consider finding the softest springs you can and run very light weight oil (maybe 2.5wt) at a very low level. You might even try them with a spring only in one leg and damping only in the other leg.
The torque on a modern trials bike isn't all that impressive really. They scoot ok off the bottom, but I doubt they really make a whole lot more power from low rpms than say a 250cc two stroke MX bike and they might actually make less (the gearing is so dramatically different its hard to tell - 4th on the trials bike is probably something like 1st on my CR). Main difference from a MX bike is that the trials bike runs really clean and smooth from very low rpms where the MX bike would be unhappy, blubbery and prone to loading up and fouling. The trials motor is ultra-controllable with smooth, clean, linear response. Its all about control, when you have super-low gearing and a 160lbs bike, you don't need much power at all. Also the flywheel is very heavy so if you need a quick burst of power you just get the flywheel spinning (rev the motor) than take advantage of some of that stored energy in the flywheel. If you watch a video of a pro doing a big splatter, especially on a 125cc bike, you'll note that the rider revvs the motor out very high with the clutch in before doing anything. When you've got a heavy flywheel spinning quickly you can dump an enormous amount of power into the rear wheel for a quick burst.