Hi All, first post and question. I've been told by my mechanic that I have a 3/4 ton - ton frame under my 1500. It has a couple of plastic tabs in the frame marked HD and I have noticed in my repair manual that there is a C3HD model. It is not mentioned often in the manual is this a "rare" thing? My VIN say's that my truck is just a normal 1500 but looking at the suspension you can tell that it's beefed up. If this is a heavy half would there have been any engine modifications to it? I would like to put a 383 in it as the 5.7 has 204,000 on it and is getting a little tired( doesn't burn oil though!) Any thought's on this being a rogue model? What have I got exactly? Any suggestions on the 383 swap? I will probably keep the stock 5.7 and re-build it and swap them as necessary. Thanks!