8 3/4 guru need your help

Been using the same 742 casting with the same 4.56 gears since 2006...no bracing ...no billet yokes......904 with transbrake....engine on two step at 3000 rpm....brake releases 5000 rpm....

Broke the 40 yr old stock driveshaft earlier this year...

check the racing section...Dart just went 10.33 in Bakersfield...with same old 8 3/4