Do I have to buy an IP kit or FB kit? or Can I just get better gears put in? I currently make 457/300 to the wheels. I have no clue on what I should do. my axles are fine but do they still have life in them or should I go all out?

 

have you think about the Puddymud diff ? check on the forum here , its cheaper than R200 nissan swap or
Ford 8.8 . stage 2 puddy diff good for 400whp+ was 1600$ i think