What kind of line pressure are you running. I use the machined down retainer plate like you have in your picture and never broken one. I build a ton of 47/48 RE Cummins transmissions with up to 220 psi and the plates hold up fine. Stock inputs, nope. I always check pressure once they are back in the vehicle, get some good gauges and go through the pressure tests before you drive and you will prove everything is correct.
