99 Silverado 4.3 Tranny Am I being tricked? 4L60E\4L65E

[FastGM500]

I tried doing some research and found that the L60 and the L65 have the same cases with a little different options such as an extra planatarry gear and some extra clutches. So in conclusion you could build a L60 into a L65.

I have an M30 code on the sticker in my glove box which meens its a 60L
Tranny shop says its a 65L

the core prices are different the 65 is $250 and the 60 is $139 does something seem odd here?

the 60 comes out to $1026 to my door and I get to keep my core
the 65 come out to $1200 with me having no core.

whats going on?

99 silverado 4.3