I just removed the trans from an 01 5.9 magnum and the flex-plate has the senser pickup flange-holes around the edge. Converter has no weights and no weighting on the flexplate that I could see either. I do have the right B&M flexplate on my 05-5.9 hanging on the engine stand. I know the pistons are different in the 360-380 hp engine, maybe why a regular plate is used. I'll try to weight the difference between the stock and 380 piston.
I guess the crate motor could have a different balance factor,odd that the crank balancer is for external balance and a zero flexplate.As someone said it could be partialy internal balance. [/quote]
Meant to add the stock piston are dished and the 380 is flattop with those coated inserts on the skirt.
