Very similar to the 4905 which had slightly updated driver's area and electrical. Long wheel base two axle rides very nice, but has a wide turning radius, so plan your turns. One of the highest volumes of baggage storage areas of that era.24 volt electrical, 8v-71 engine. Very many GMC models have common parts. Windshields fit 41 through 49 series and Prevosts. Nice compact drive train, which is easy to maintain. except for the starter, which is in a restricted area. Which automatic trans is in this coach? If it is the VS2-8, you will get good fuel mileage on the interstate; some reporting as high as 10mpg.,with a top speed approaching 80mph. Since it is only a 2 speed, it sucks on hills which require a downshift. Think of it as a 3 speed automatic with only 1st and 3rd gears. That tranny is obsolete, although parts are still avail, but getting scarcer as the years go by If it has the newer 3 speed V730, you are fortunate as it works quite well in that coach. Unfortunately, that model drops fuel mileage down to 6 to 8 mpg and limits top speed to about 68 or 73, plus or minus depending on governor setting.
Power steering is a desired addition to this model. Great coach to have if in good condition, with a sound engine and trans. If the engine is tired, you might want to keep looking unless the price is really great.
GMC's have fewer rust issues than the other brands of that age. Look for floor buckling or rotting in baggage area ceilings, where the door spring hardware attaches. You also need to get a good look underneath (safely) with secure blocking or a pit if possible, to check brakes, drums, air bags, leaking wheel seals, king pins, steering play, strut rubber bushings, body issues from cracks or salt corrosion at suspension attachment points. Of course things like wipers, lights, controls, quality of conversion, heating system, radiator, rust out around drivers window and astro windows. Check for any serious buckling above wheels in the siding. This usually happens if the coach hits something of mass either forward or backing up at idle speed, as those spots would give first. There are other things to consider, but these are the main ones. Pics?
I love my 4905 and wouldn't have any other except a late Prevost maybe, if I win the lottery big.