Which belt? How do I know what size alternator I have?

In order to get the right serpentine belt for my 2000 Silverado 5.3 Z71 I need to know which alternator I have (100 amp, 105 amp, or 130 amp), how can
I find this info? The alternator doesn't have any markings visible while installed. The original belt is a GM 12554029 URN 6PK2345. I'm trying to find the belt on rockauto.com but that number isn't on any of their selections.
Thanks for any help, Al
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ajtessier wrote:

My 2000 Silverado Z-71 5.3 LT orig belt is GM 12554029....
My 'quiet' replacement belt is: Good Year Gator Back Poly V 4060922 6PK2345
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ajtessier wrote:

has the A listed on the side of the alternator, its a thin white paint so you don't see it unless you know its there.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for your help. I have the 105 amp alternator and I found out that the part number I posted has been changed by GM at least twice.
Al

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.