HUD Codes will be built upon a permanently attached steel frame. Some may be hy-brids with recessed steel frames, but the steel frame is always there and is the most visible means of ID. Roof trusses of HUD codes are often very different, but as mentioned above are seldom visible. Mods look very much like stick-built in basement appearance, but will always have a built-up beam running lengthwise between major components located at what is called the marriage-wall. Data plates are only found on HUD Codes and they are "plates"-small metal tags, painted red with embossed/engraved lettering affixed to the exterior of the home. Data sheets are supplied with all HUD codes, typically (nowadays) affixed to the wall or door in the homes largest closet. This information details what environmental zone the home is constructed for and gives handy info such as r-values, major appliance brands/sizes etc. Lastly, mods are constructed to meet the state building codes for where they will be sited and HUD Codes meet national manufactured home standards. And, as mentioned above, mods frequently are better built than stick built - after all, they need to travel the highways at 70mph on their way home[]......Greg