The small block Mopar with an auto trans is about 100-150 lbs lighter then the flathead 6 with a 3 speed. When we pulled the flat 6 out of my son's 47 and installed a 360 auto, the front end lifted about 4", when I put about 1/2 my weight on it, it was back at the original hieght and I'm around 250 lbs. Gene