when i run the numbers for the 427 and keeping current compression with the 408(10.65) the 427 losses 6hp but gains 6 ftlbs tq. bump the compression to 12.0:1 and gain 17hp and 24 ftlbs tq over my curreny 408 combo. this 427 combo would cost me about $2500 to do using most of my 408 parts. i think i'll pass on this combo.