I was wanting to know if theres anything to look out for on my 2007 Mustang Gt manual 5 speed with Shaker 500 sound sytem. It has 117 thousand miles ive had it for about 5 months now. Any reliability issues or anything like that before i start putting mods on it

 

You might want to post your question in the 2005 -2009 section as this California Special section is rather quiet. If you have a CS, it is basically an appearance package and will be the same as any other GT mechanically.
As far as reliability, it all depends on prior owners and the maintenance. I have less than half your miles so I may not have the best input for your question but I have had zero issues since I bought the car new.

 

Is your 2007 also a California Special or just a regular GT ? Your post doesn't mention anything about GT/CS..

 

There are a few things. Check the interior fuse panel (Smart Junction Box) for corrosion --it runs most of the car and will go haywire when it gets wet from an interior water leak --- oh yeah that's another thing to look out for The alternator might go around 100k, don't bother with aftermarket replacements, go for a 3 phase unit from a 2010+. I think those are probably going to be done of the more likely ones, but if you search around there's a few threads on common issues. A few to search for that comes to mind are cam phaser rattle, 3rd gear lockout issues, and weak upper strut mounts