if I were you I'd start out running what you have installed, and see what you think. From there you should be able to gauge whether you should gear up or gear down and determine from your impression on where to go. I would also take a look at how your car performs compared to others and ask them what they are running if they are running a tc4 as well. That's just what I would do. I think the 72 is a good starting point and it's not worth switching the gear out unless you know it won't work.
well the thing is that i dont have anything installed yet, im not even sure where to start out for gearing a 19t in a tc4 in general, i did some google searching but mostly found threads about brushless gearing.