My bro and I did a financial analysis of this a few years back. The Stage V heads are a great product and will produce more power than an original 426 head will, and you can build a 440 Hemi for about 2-3 grand less than a buying a crate 426. However, with the few grand you save, you have to perform a number of block mods that are not a lot of fun and if done incorrectly, could eat up that saved $3k quickly if you sub them out. Among those mods are notching the block and welding in a half tube into the lifter valley to provide push rod clearance. With the additional power levels, you also would need to add cross bolted main caps, which is more machining expense as well. You also need to add oil return lines to get the accumulated oil out of the heads and back into the pan because the size of the Hemi head over the 440 head is significant.