Does a 2005 Chevrolet 2500 hd 6.0 liter have an Allison transmission?

It looks like 2005 was a transition year between the 4L80E and Allison 1000 with 6.0 engine. Sounds like 4L80E was typical, but easily upgraded to Allison at time of ordering, but also depending on packages and equipment.

If it has an external filter it is the Allison, otherwise it is 4L80E version.