the VCT limits your valve spring\camshaft options. once you get to stiffer springs it starts screwing with the VCT since the cam timing is adjusted and sustained by oil pressure. too much spring pressure and the phaser doesn't have enough oil pressure to hold steady cam timing. if you're running high lift cams then you can't afford to have unstable cam timing...the stock phasers allow for up to 60 degrees of retard so if that happened at 7500rpms in my engine it's toast.
anyway you'll gain way more power by using aggressive cams+springs than by playing with a couple degrees of cam retard\advance. plus it's added protection.
i don't have any more info on the V10 gears but i think blow by racing actually sells them. i may be wrong about that but i know we have a vendor here that uses them in some of their builds. that info wasn't out when i built my engine or i most definitely would have used them.
