Welcome aboard!

As I recently reminded someone doing a different swap, keep it simple. It can be done, and it isn't uncommon, and it doesn't have to be complicated. Choose an engine platform compatible with the same year model, complete with all the accessories and drive/belt system, and swap it in along with the wiring harness and ECM featured the same as your truck. You'll also need coolant hoses and other plumbing accommodations, such as the gasser fuel pump, which can be either in-tank with the OEM fuel sender, or independent external (the Diesel fuel pump will not work). Transmission control, if an auto, is in the ECM, which makes that an important part of the swap. The Diesel computer is not compatible with a gas engine, in any form, unless the engine and transmission are either mechanical or independently controlled. Everything will fit, but it all has to speak the same language at both ends.

That said, consider the engine series generation to choose, if your emission rules allow. The 1996+ model years offers greater computer options, control and monitoring, as well as greater economy and power with the Vortec series. The series' also improve over the model years, with options for PFI vs. TBI fuel control. The auto transmission will also have to follow the technology series. 1999+ allows options for expanded engine series, including the 6.0L and 8.1L. Ideally, you will want to source a donor truck, and do the swap, side by side, whichever you choose.