I don't think you really need tanks at all pvt. If you think about the cost (in terms of resources+time) of the techlab and any upgrades, you could have an extra couple of barracks and more bio.
I think it's worth trying opening with 2 rax pressure (i.e. you poke at their ramp, try to kill some stuff, but back off as soon as it looks like they have better numbers), and increase your rax count to 5 with a reactored starport. If the protoss makes a *single* mistake with a forcefield, you will win.
Generally, against this sort of build, I have to just play for time to get colossi. If they are four gating and get kettled in, you have map control and can expand. Then keep the pressure at their front up while you harass with 1/2 drop ships. Once the game gets past the 10minute mark, you will want to have expanded, and added a second reactored starport on to pump vikings if he gets > 3 colossi out.