We play a homebrew game called High Octane which is basically Gorkamorka (core rules) with some adjustments: humans instead of orks, different weapons and points costs, as well as some house rules. Played as a campaign it focuses mostly on gangers with the vehicles being mostly for transportation. For recreations of Mad Max I think it would work well. The vehicle movement rules are great as are the rules for boarding and ramming and such. We use 28mm scale with 1:43 vehicles. There are some battle reports onthis forum if you look for "high octane" but I'm afraid I don't have a working link to our rules at the moment.