If you are looking for local read - Holding the rebuilder accountable search for a "Diesel Injection Shop" I am sure NJ has plenty of them around. If you are looking for a shipped option Diesel Injection Service has the right (high dollar) test equipment and somewhat reasonable prices on exchange based rebuilt pumps.
The stock mechanical 6.2 pump is capable of somewhere around 225 horsepower. The only significant increase pump wise is when you go with the "Marine" pump which has larger plungers and more fuel delivery capability. The Marine 6.5 pumps are capable of 280-300 hp. This much fuel and and power without supporting internal engine mods is not recommended.
There are numerous versions of the mechanical DB2 injection pumps for the most versatility ask for the j-code spec pump. It will have large plungers and allow for more fuel delivery.
Stay away from the Ebay rebuilders. They dont have the test-benches to check injection pump pressures like the big companies do.