BIG BLOCK ,WE DONT NEED NO STINKIN BIG BLOCK, Just fun'in, Stay SBc,you've got the headers, etc, AND THERES A BIG weight difference.Stock block,build a 406,there killer motors! Or for a little more (aftermarket block) which you will NEVER be sorry you bought!!! Build a 454sbc,YES 454 SBC,Ill run any comperable (sp) bbc .You also already have a nitrous setup for the combo now WOW what a blast! And its easy on parts!!! Ive got a 472 SBC and its GREAT!!!!!!!!!!!!!! D.R.