Help me win this argument 400 in a 72.

I say big block, but it is some work. I've got a small block A-body (68 GTS convertible 340/auto) and both of my sons have big block four speed A-bodies (67 Barracuda fastback and 67 Dart GT convertible). None are road worthy at the moment, but I have never driven anything near as fun as my son's Dart. For many reasons (including so that my wife can drive it) my Barracuda convertible is getting a 727 behind the 440. So, you know where I stand and I've got a spare, buildable 340 sitting in the garage...