Actually, a unique feature of PAF is that almost everything it gets is customized. Even when we got the blk 15 F-16s in the 80s, they were customized and were slightly different from the standard blk 15 that were sold to other countries.
Even now, the MLU PAF F-16s are getting are customized rather than standard MLU-3 or MLU-4.
Let me try to explain
MLU-3 in made up of the following.
Automatic Target Hand-off System (ATHS)
Integration of anti radiation missile capability
Integration of target designator system
Further implementation of the Digital Terrain System
Integration of the Link-16 system
Integration of capability for GPS controlled weapons (GBU30/32)
Introduction of Helmet Mounted/Cueing Sight
Introduction of NVG compatible helmets
Where as the MLU 4 Tape has the following features which PAF is not aquiring because of financial crunch,
M4 tape contains in addition to above:
Introduction of advanced short-range missile, as a replacement for the current Sidewinder (AIM-9X, IRIS-T)
Integration of advanced Link-16 functions
Integration of SNIPER targeting pods
Here's what PAF is getting:
The Government of Pakistan has requested a possible sale of 60 F-16A/B
Mid-Life Update (MLU)modification and
Falcon Star Structural Service Life Enhancement kits consisting of:
APG-68(V)9 with Synthetic Aperture Radar or APG-66(V)2 radar;
Joint Helmet Mounted Cueing Systems;
AN/APX-113 Advanced Identification Friend or Foe Systems;
AN/ALE-47 Advanced Countermeasures Dispenser Systems;
Have Quick I/II Radios;
Link-16 Multifunctional Information Distribution System-Low Volume Terminals;
SNIPER (formerly known as AN/AAQ-33 PANTERA) targeting pod capability;
Reconnaissance pod capability;
Advanced Air Combat Maneuvering Instrumentation Units;
MDE included in the MLU modification and structural upgrade kits
21 ALQ-131 Block II Electronic Countermeasures Pods without the Digital Radio Frequency
Memory (DRFM) or ALQ-184 Electronic Countermeasures Pods without DRFM;
60 ALQ-213 Electronic Warfare Management Systems;
1 Unit Level Trainer; and
10 APG-68(V)9 spare radar sets.
So you can see that everything there is just a customized upgrade rather then a MLU-3 or MLU-4. The only thing missing is integration of AIM-9X sidewinders(5th gen) because we are getting the AIM-9M sidewinders (the latest ones before the 5th gen).
Hope that explains it...so it is blk 50 standard
Here's a link to exactly what PAF is getting
http://www.dsca.mil/pressreleases/36-b/2006/Pakistan_06-10.pdf