I assume you are referring to a Limited Slip not a Locker.
I have a Locker installed in my mustang and it is insane.
It is the Powertrax Lockright locker. It does not require a gear set up, and uses basic hand tools
to replace the stock spider gears.
It is downright violent with traction.

I will be selling it soon (complete 7.5" rear) with it installed and fresh royal purple.
Only because I came into an 06 8.8 for cheap, and my friend is installing the 3.73's for me.

The Ford t-lok should be fine for you unless you really start building power.
And you might want to have some 3.73's or 4.10's put in at the same time.
If you really want to beef up the car then go with a tru-trac or detroit or just swap it out for an 8.8 or 9"

 

what i posted above, the tlok is no stronger then your stock open diff, i blew up my open diff on a 100% stock 02 3.8 AUTO vert, the slowest combo available,

 

Hi all, Im looking for a website where I could buy a locking diff for a good price. The only places I found the lock prices where around 450-500 $ here s one of them :

http://www.drivetrainspecialists.com...ruetrac-1.html

Anyone knows any place where I could buy it for a cheaper price (but not despite quality)
thx

 

Unless you are doing a build of the engine for power with a turbo or other power adder, you really don't need a True Track. And building the 7.5 to handle the power would be a waste of money in the long run.

Just get a take off 8.8" rear end and swap it. Stronger than the 7.5 to begin with, comes with the tlok (which is likely all that you need), and in the long run will be cheaper than buying the parts and installation cost for a weaker 7.5" rear end.