It really wasnt. The biggest part was re-routing all my existing new accessory and stereo wires out of the way of the new pedal swing. Surprisingly the upper mount studs were in place from the factory. Even though a clutch pedal was never put into this 4-door body style. I had to get an 90 degree angle drill to cut the necessary opening through the firewall, which GM also had marked out with a punch in the center to make it easy. My hole saw stopped cutting 1/3 of the way through though and I had to file the blades back three times before I got through the firewall. Also I didnt swap out the brake pedal. I just cut it shorter and used the proper pad from the donor truck.
My new 400 flywheel arrived today. I have been following 88GMCtruck's swap over on GMFS for info. Seems he went with the Hays 90-103 clutch and loves it. The clutch is listed for diesel applications and the jegs page says that even though its got a larger than OE disc, it will fit on the OE flywheel. Im still skeptical how this is possible because a 12.25 disc overlaps the threaded pressure plate mount holes.