Caphawk,
I have a dingo 285, and i dont think that that particular model came with hex rims?, but you may be off on the model number? The hex axles I have seen usually have threaded circular ends. They need hex Hubs on them, which are secured by a large nut on the circular end. The hub typically has a 4x4 bolt pattern to fit an 8" steel rim.... post pictures if you can?
18" knobby offroad tires that fit 8" rims $80 shipped
http://www.ebay.com/itm/Kenda-scorp...atv-/201012915784?hash=item2ecd4dae48&vxp=mtr
Steering wheel: the part number is 6038, it is obsolete, you can, however, look for a steering wheel here:
http://www.bmikarts.com/Steering-Wheels_c_275.html
Brake pads (assuming disc brakes? not brake band?)
These are like the universal mechanical disc brake pads
http://www.bmikarts.com/Brake-Pad-for-Mechanical-Caliper_p_603.html
Headlight/spotlight ideas:
walmart actually has some smaller/nice LED fog/offroad lights in the automotive section, which can be wired up to a 12v battery (lawnmower size battery, or automotive) You will have to charge the battery on your own though unless u buy a special kit for the greyhound engine so it will put out 12v when running. Im clueless on that
this place has a nice light thought not led, cheap
http://www.northerntool.com/shop/tools/product_350960_350960
what you need to do for the greyhound tank is download the manual and scroll to the end where there is a parts breakdown.
http://images.harborfreight.com/manuals/66000-66999/66015.pdf
call harbor freight and ask for their parts department, reference the engine model number (should be a sticker on the engine shroud somewhere with that info, the manual probably has it too if it looks the same as yours). I ordered parts a few years ago for a kart that had a 6.5 hp greyhound engine on it and I think that the tank cost like $14 or something like that, came all the way from china though.