no you can't get a decent 4.25 inch bore out of a 396....you can put a 4" crank into it though(instead of the 3.76")...that makes around 440c.i. a little massaging of the lower cylinder bores and maybe along the oil pan rail might be required to clearance the crank...it's simple,just be careful not to take too much off(you only need about .050)... i believe an oil gallery runs along the bottom of the pan rail...