none! you don't make anywhere near that kinda of power to need bigger injectors....maybe after some heads/cams/ blower you will need larger injectors...until then stock is fine.
There is no advantage to it with your current mods. Plus I THINK the cobras use the taller style injectors in which case the harness would be different.
The nitrous kit should be able to work with your stock squirters. As everyone else stated, the 39lb/hr injectors are not what you need. Skip them (no matter how good a deal they are) because they're not warranted....not to mention it's going to cost you what you've saved in the price of the injectors and then some to have your ECU recalibrated in order to use them!
They are different and wouldn't fit anyway. You would need a set of plug adapters like this but the other way around. They are $119. So a $100 set of injectors becomes $219. Not worth it.