LSX fuel injector info
Ls Series motors have had a few different types of fuel injectors already.  They also run at higher psi then most vehicles which is important to know as well.  When deciding which injectors you are planning on running you should take many things into consideration.  First we'll discuss the connecting plugs and what motors use which type.  Then we can dive into the fuel pressure rates and finally we will look at some formulas to figure out the size you need! 
                                             INJECTOR TYPES
These were used in the original Gen III LS1 and LS6 motors as well as the Gen III truck motors.  They are the tallest of all LS Series motors and generally rated at 3 bar (43.5 psi). 
USCAR INJECTOR  (LS2) - These were used in LS2 engines and are slightly shorty then the LS1 injectors.  The USCAR connector is a Gen IV specific connector.
USCAR INJCETOR (LS3,LS7,L92,L76,L99) - These are just like the LS2 injectors but they are very short.  Much shorter then the LS2 or LS1 style injector. 
                                             FUEL PRESSURE
4 BAR -
Ls Series motors run at 4 bar when most cars and other injectors are rated at 3 bar.  What does this mean to you?  This means that any injector that you buy rated at 3 bar will product much higher ratings once in your higher PSI 4 bar system.  1 bar is equal to 14.503778 psi.  So 3 bar comes out to around 43.5 psi which is the most common.  The LS series systems running 4 bar comes out to about 58psi.  So if you have a 42# injector rated at 3 bar once you place it into the higher 4 bar psi you get a 56# injector.
                                      LOW OR HIGH IMPEDANCE
These injectors run more ohms and are safer for your vehicles on board computer.  These are what all LS Series motors run.
LOW IMPEDANCE - These injectors run less ohms and will fry your stock ECM.  They are for aftermarket controllers only!!!
                                     WHAT SIZE FOR YOUR CAR?
Take your target peak horsepower and multiply by
- .5 for naturally aspirated
- .6 for supercharged engines
- .625 for turbocharged engines
2. Take that figure and divide it by number of cylinders
3. Divide by .9 (for 90% duty cycle)
This will give you the number you need for lb/hour for each injector
EXAMPLE - 700 Horsepower Supercharged engine (700x0.6=420) (420/8=52.5) (52.5/0.8=58.3) So this application would require a 58.3lb/hour or larger injector.  As a general rule you should always go to the next highest size.