From bottom to top:

Loader addon (from D-538, will be published as a standalone mod to also be compatible with base game B-66)

Fuel Cistern / Fireproof Exhaust addons (from B-131/C-375)

Short Log Carriage (it's actually the C-class Log Carrier intended for Medium Logs, but it's used with the C-66 for short logs instead) (2 load points)

Log Carriage with Crane / Medium Log Trailer (4 load points)


Some additional modifications have been made to the truck itself, mainly to make pulling the medium logs a little easier.