Carter, no need to use inaccurate small scale monster truck tires unless you're after that look
The SoReal tires can be had separately, or there are resin casters out there doing offroad tires, looky here:
http://www.magazinepublisher.com/models/tires/tires.html
http://public.fotki.com/cnaind/truck-tires--wheels/off-road--pickup-tires/
http://www.ebay.com/itm/SoReal-Interco-TSL-Bogger-1-24th-Scale-Model-Builder-Tires-1-3-4-OAD-8-Pack-/150906572409?pt=Radio_Control_Parts_Accessories&hash=item2322bb8e79
http://www.ebay.com/itm/SoReal-Interco-TSL-Bogger-1-24th-Scale-Model-Builder-Tires-1-3-4-OAD-4-Pack-/200817920326?pt=Radio_Control_Parts_Accessories&hash=item2ec1ae4946
You can check out our offroad specific build forum for tips, tricks, and anything else 4x4 related, the linky's in my signature below