first of all whats wrong with the ute diff you have? the h165 ute diff is quite strong and reliable being able to withstand up to about 125 kwatw. i would recomend keeping the one you have and spend you money on other upgrades.... but if you do want to fork out the cash usually about $1000 you can upgrade to somthing like the r31 diff or the commodore diff even a vannette diff. have a look thru the tech section as its very helpful

edit: you beat me to it