My experience so far...
I have a 2001 5.7 Captain's Choice (330hp MPI) with a fuel pump challenge.
This was an early generation MPI...there is no fuel control cell on the front of the engine (black canister).
There is only one high pressure, high volume fuel pump on the engine (compared to 2x on the newer ones..a low pressure inline, and a high pressure in the FCC).
It is mounted on the port side of the engine in a water cooled housing (pic attached). The pump is stamped with the following Pierburg p/n: 7.21659.02.0
According to the Crusader parts list, it is identified as Crusader p/n: 47039.
After a week of scouring the internet and calling various shops, I have learned that most vendors will have a different Pierburg pump listed as Crusader p/n 47039. The replacement must be the same exact dimensions in order to fit in the water jacket.
Most are incorrect for my engine (verified by the Pierburg p/n); the replacement most vendors are carrying is Pierburg p/n: 7.21565.71.0 (pic attached) with a removable rubber jacket.
The pump is 1.5" too short and the inlet port is larger.
I have spent a lot of time trying to find a replacement. These days, trying to find a part by mfg's part number is impossible. Most parts stores can't help you if you cannot start with the year, make and model of a car.....good luck if you say it is for a boat!