Made an upgrade of the 9398 with XL motors and gave it 30% more additional parts. This is my MK2 version as my first upgrade was not as successful. Also it uses
Lego # 9398 Technic - 4x4 Rock Crawler Truck B Model *PLEASE READ* | eBay
LEGO® Technic: Monster Jam Dragon Truck 2in1 Set | 42149| TimbukToys
Ultimate upgrade for the 9398 4x4 crawler with pendulum steering (no servo needed). I also made a pendulum steering file in the rebrickable link you can download and have a closer look
LEGO Technic 9398 4x4 Crawler MOD | Nikolay Gamurar | Flickr