TB's arn't a necessity...may people have done them on carbs.

whats your intenede use for the engine may help others sugest a comp rati...as if its an out n out track car you could use race fuel etc.

also, i heard you have to do a lot of headwork as cossies are turbo so air is being forced in wheras and N/a engine likes to breath...dunno if thats right...someone more experienced will probs correct me