'00 Suburban 5.3 : fuel pump & pressure regulator choice help needed

Hi
I own a '00 Suburban 5.3 VIN 3GNFK16T4YG165432
I need to change both parts :

Fuel Pump :
http://www.rockauto.com/catalog/x,carcode,1361517,parttype,6256
ACDELCO Part # MU171 {#25315983}
or
ACDELCO Part # MU1443 {#15759666}

Fuel Injection Pressure Regulator :
http://www.rockauto.com/catalog/x,carcode,1361517,parttype,6124
ACDELCO Part # 17113700
or
ACDELCO Part # 2173073 {#89060420}

But I dont know what is the right part ?

Thank you.

Christophe Salvaing

Don't trust the serial number method of ordering fuel pumps on the '00 and early '01s. I got the wrong one and had to buy a second. If you can, drop the tank and see what you've got first.

As it asks in the description, you need to know what the code is on your fuel pump. You must remove the pump to get the code. It's on a little white sticker on the pump module.