quetion about mounting tweeters in my car

You're talking about time alignment and yes, it can be an issue if the woofer and tweeter are placed too far apart.  What happens is the sound from the tweeters (which are usually placed much closer to your head) arrives at your ears before the sound from the mid-woofers and you can hear the delay.  In the close proximity of a car, it is usually not that noticable.  Without specialized equipment to test it or to adjust the timing in your system, the only thing you can do to mask it (if you think it is a problem after you mount your speakers) is to attenuate the tweeter signal strength by inserting a resister L-pad into the signal path between the X-over and the speaker.

i'm guessing for the most part then i will not have to worry about it.

out of curiosity how far does the tweeter and woofer have to be in order for this to take place???

Personally, I would not worry about this phenomenon. If it was important to you, then you would be working as hard as possible to minimize it by putting the tweeters somewhere else. What looks good on a meter or scope may infact not sound good to your ears. Solid advice for the factory tweeter mounts, you may want to consider a wrecking yard as well. If they are the wrong color, who cares, nothing that spray paint can't fix.