The NV4500 came stock behind 8.1L engines in the old body style 2000/2001 HD trucks. The flywheel, pressure plate, pilot bearing etc are the same as all the old school SBC/BBC internally balanced 168 tooth stuff. The OEM flywheel has metric pressure plate bolts and dowel pins for alignment. If you order the factory GM part number for the pressure plate you'll get a Luk SAC clutch cover. They can be a PITA. I decided to go with an old school diaphragm pressure plate with the mounting holes enlarged to fit the metric hardware and drilled for the dowel pins, OEM 8.1L/NV4500 flywheel and a 10 spline clutch disc to fit my transmission's input.
You can use any GM NV4500 bellhousing and an 85-91 square body hydraulic clutch and master to operate either the internal or external slave depending on what year of NV4500 you run. You'll need to make your own hose to connect the two, but the aftermarket has all the fittings needed to put a -3 AN hose between the two. Of course you'll need a high hump transmission tunnel to clear the transmission. You will also need to update the tuning on the engine to suit as well.