The 8.2 uses a unit injector system, so no injection pump to turn up.
You can get more power by changing injectors, nozzles, and adjusting the injector height(timing).
Most in the know wouldn't recommend modifying an 8.2. They weren't all that reliable in stock form, and turning them up didn't help that. If you do any upgrades to one, I'd choose a better turbo and install an intercooler as well.
If you're going to swap in an engine, why not choose something bigger/more hp then a 3126? Unless you're using a donor bus, most of your work will be custom anyways, so go big.