After looking at their website  ,

The two Bradley offerings they have are the one that comes with the interior which is an M2  , stock # SS-004

Or ,

The M3 which doesn't come with the interior  , stock # SS-006 .

They make that interior kit that is sold separately for the SS-006

I can't get the supplies page to load on their website so I'm going off what you submitted above .

It's common for interior upgrade kits that are sold separately to contain extra / more variations in components .

I don't know anything about the Bradley so maybe the M2 doesn't have the same interior equipment and that's why there are differences in the upgrade kit for the M3 .