Hope this helps...lots of good info on LS1truck forum.
Bolting up a manual tranny:
This was the first thing I needed to make sure of. It seemed all the forums had vague information and most people were not getting the answers they wanted about the swap. "Do it like this and it will work they said". I needed to be sure. I didn't want to have to pull the heavy NV4500 back out because I didn't do my homework. After nearly 6 hours of browsing forums I learned that the 99-2000 LS engines had a shorter crank than the SBC engines. Later on they became longer but were still a pinch short. Advance adapters sold a kit for nearly a grand but that was outrageous. The large price was because of a smaller bellhousing that would make up the difference in the crank length. An SBC clutch will bolt to the LS Flywheel as long as the dowel pins are removed. The only issue with using an LS flywheel is that the bolt holes are metric and the holes will need to be reamed out on the pressure plate. There was also an aftermarket flywheel for the cheap that was more designed for mating old trannys to the new engines as it was standard thread for the pressure plate bolts but metric holes for the connection at the crank. I went this route. Also the pilot bushing is different, use one from an LS2. Of course I had to wait until the flywheel and pilot bushing arrived and then take measurements to confirm. I probably dug into this too deep as I actually measured and confirmed the face of the new flywheel .2” closer to the engine and the pilot bearing .13” closer to the tranny. Since the input shaft end is very long, the pilot bushing was of no concern. At the time of the installation, all I could hope was that the .2” of clutch engagement would be made up by the hydraulic system. Once I was able to drive the truck, my presumptions were right and everything was fine. I was able to use my old NV4500 bell housing, clutch, pressure plate and slave cylinder. The only new purchase was the flywheel, flywheel bolts (don’t reuse old) and pilot bushing. It should also note that since the LSX engines are all metric, the bellhousing bolts I had were no longer going to work. Also when putting the engine on the engine stand, I had to dig up metric bolts to make the connection. Since the LSX engines don’t use one of the upper bellhousing bolts, I chose to move the upper arm on the stand to the lower bolt hole position, thereby keeping 4 bolts connected. Since I have the first gen NV4500, I have the external slave cylinder. This bolted right up, but was very very close to the plastic plug for the oil level in the oil pan. Most of us doing the conversion will not need to plug anything in here. If you plan on using it, make sure you don't have an external type slave cylinder.
the thread is on ls1truck forum here.
http://www.ls1truck.com/forums/lsx-...-gen-i-nv4500-conversion-detailed-part-s.html
