It really depends on what you are doing. Anything below 900 hp then a 12 v head should be fine. It costs 80 dollars to get a 12v head over 4000 rpm and its costs nearly $2000 for a 24v to get over 4000 rpm saftely. If you change the head you also need to change the piston (because of the placement of the bowl in the piston), the injectors, the inj. lines, etc small stuff. Not really needed in my opinion, but to each their own.