Hi,
on the 708's you've got to be thinking about the high 160's, maybe early 170's, but you've got to watch the injectors, they're probably at their limit at that point.
You'd want a 4-1 or 4-2-1 manifold and proper exhaust (supersprint?) to go with it.
If you go the harder cam, and pistons, you'll want some headwork to go with it and you'll be over 180bhp and needing those injectors.
Don't forget about the clutch at that power...
If you're 1-plug, my Predator ECU is on group-buy at the moment (see Datashift Affiliate Section), £550 fitted and mapped and it'll easily support TB's
Kind regards
Andy