I have a Fender Standard Stratocaster. 3 Single Coil Pickups.

I am going to be putting a double coil humbucker in the bridge posisition. Already checked the routing and there is indeed room.

I am wondering 2 things...

1. How much will putting a good Humbucker in this Made in Mexico Fender Standard Stratocaster improve the sound? I have heard from some people adding a solid pickup to the MIM Strats can definately make them sound a lot better, almost as good as the American Strats. Is this true?

2. I absolutely love the sound of the American Fender HSS Strat, Fender HH Telecaster, and that new HH Jaguar.

I love the bright tone of a fender with double coil pickups - what pickups should I buy that will allow me to most closely replicate the sound of a Fender American Strat on my Fender Standard Strat?

I will be buying a new guitar soon... but I am going on tour in a few weeks and need a temporary fix for the next few monthes. I don't have the money, or a final choice on which Fender gutiar I want to get.

Hope you guys can help me out!
It won't really make is sound exactly like an American Strat. It will make it sound different than it does. I recomend a Dimarzio PAF Pro. That pickup fits almost any setup in amy position, works well with single coils and can support most styles of music (unless your playing really thick Death Metal or something, but I'm assuming that since you are playing a 3 single coil strat that you are not playing anything that "heavy").
Out here you've gotta know where your towel is!
Yeah. I'd say think new Foo Fighters, except maybe a bit brighter tone.
I believe this is what they use in the American Standard HSS Strats. That's probably gonna get you the closest to the tone you are looking for.
Heads will roll. Throats will be slit. Blood will flow like springs of water.
It will definitley improve sound and provide some versatility. I would go HSS and keep the single coils. I recently swapped out my stock HB in my MIM Strat and I felt it was a nice improvement. I originally got a Seymour Duncan JB but now find it is a bit too bright for me so they are swapping it out for a Custom Custom TB-11 via the mail.

I MUST recommend Duncan due to excellent service I just got this.

I can't say it is going to make a MIM sound like a MIA though as there are other differences in hardware but if you are on a budget - this is the way to go. Good luck,