Hello - just found out the hard way - when you change automatic transmission from GMC Turbo-hydro to the GMC type powerglide or vice-versa the flywheels are NOT the same - the hub on the side of the flywheel that the flex plate bolts to is 3/16" shorter on the Turbo Hydro than the Powerglide. When I rebuilt my 351E I had it balance with a Turbo-Hydro flywheel instead of the Powerglide that I'm using in the 1965 Suburban - so I needed to have the machine mill a 3/16 spacer to bolt between the flex plate and flywheel.
