These are FSX dds 32-bit textures only. The HTAI C99 model with cargo pack is required. It can be found at http://htai-models.com/downloads.html –
http://htai-models.com/downloads/models/ai_beech_c99.zip
The HTAI Beech 99 model has been updated by Gavin Cole (gavinc), Graham Eccleston (ggeccles), & Tony RD (peluso5) from the AIG Forums to adapt them for use in FSX and P3D. Get the model here:
http://www.alpha-india.net/forums/index.php?action=dlattach;topic=25048.0;attach=44837