running some more numbers for the 392 and the 427 it looks like the best bang for the buck would be to rebuild the 408 using KB icons($400) and bump compression to 12:1. this combo makes 625/584 hp/tq on desk top and the 427 with 12:1 makes 621/588. only down 4ftlb from the 408 rebuild which would make it about 410ci and way less expense.