Here is the Mobius kit
http://www.modelcars.com/moebius-53-trailer-with-reefer-option.html
Another kit to consider is/are one of the AMT race hauler kits. They come race ready with internal components, have the "low boy" stance and the sides are cut out for the tandems. Three versions that I am aware of, Gallee/Kraco Indycar, Coors NASCAR and Kodak NASCAR. I have all three and can shoot some parts pics if you like. They are not hard to get and at or below the Mobius kits.
Here are a pair available from a seller with a excellent reputation
http://public.fotki.com/Goodguyinar416/nascar-model-kits/nascar-race-car-haulers.html