I haven't blown up a 904 during 35 years plus of racing. I have hurt them ,once due to an out of adjustment shifter. I am not required to have a trans shield to run mid 11s but I keep it in just in case. Its a pain when changing a motor or trans but I like having the security of it.
68 Dart 410 / 904 92 D150 original owner 21 Ram 1500 Quad Cab, Big Horn , Hemi ,4x4 23 Audi Q5 16 Honda HRV