I can't give you numbers, but we pulled a flathead 6 with a 3 speed trans out of a 47 Plymouth coupe and installed a 360 with a 727. If I (around 240 lbs then) stood on the front frame (which was directly above the springs) the car returned to the height it was before we swapped the motors (this was less sheetmetal). My guess is that would put the flathead 6 with its attached 3 speed around 650-700 lbs or about 100-150 lbs heavier then a 360/727. They were not light weight motors. Gene