HaloMods "Classic" Read-only Archive

while browsing the local forums, i saw this guy have the rwarthog with humungous wheels and a new rocket launcher on the rwarthog. He also had the tank remodeled so it had i think one tread and half the size. Is this possible to do and still play in the game, if so what program can i use. I have milkshape right now. ThanXz a bunch?

Any help would be great!