New here / buying 2003 ford diesel

The "Bullet Proof" concept is not really specific. In general it refers to Head Gasket replacement with Studs. There is not an easy way to see that specific change. The only way is to look at the bold holding the head on and kind of know what you are looking for. Some other common things that you can see which are good are things like New Intercooler, New Radiator, Coolant Filter Bypass, EGR delete. This is all aftermarket stuff designed to fix some of the issues with the 6.0. A class C motorhome will be on a E series chassis most likely and if that is the case this version of the 6.0 is de-tuned from Ford to generate less heat in the confined space. The best thing you can do if you already own a 6.0 is purchase a ScanGauge II for about 100 dollars and plug it in under the dash into the OBDII port and watch the coolant temperature and oil temperature while you drive. This is the first sign of a clogged oil cooler if those numbers get farther then 20ish degrees apart. The oil temp will always be higher then the water temp. Also, if this motorhome has never had a tune put into it the head gasket and oil cooler are probably fine.