I've got a Noco GB40 and it does the job for my 3.2 but for the V8 you'll need the GB70.

@WillMartin:
Having jumper leads is useless if there's no other car nearby to jump from. The Noco saved my butt in the Molopo Nature Reserve. After camping for four days the battery was flat and not another human in sight and no cell signal. Yes, the battery was replaced soonest but it was less than 3 years old whereas the one in my Merc lasted 12 years so who knows when or where you're going to be stranded?