What type of Motor oil does a 1983 Honda vt500 shadow use? And how much?

Use only a JASO MA certified motorcycle oil. Automotive oil uses different additives and will shorten the life of your wet clutch and transmission gears. Shell Rotella T for diesel engines , both standard and synthetic are JASO MA rated.10w-40 oil is good for cold climate. 20w-50 for hot climate/touring. Synthetic oil will make your cycle run cooler and shift easier. For the engine you will probably need four quarts of oil, a spin on filter,and a drain plug washer . Pour in three quarts and check the oil level by placing your motorcycle on the center standard looking at looking at the dip stick. Run the motor and top up as needed. If changing the oil filter you will have to run the motor to get an accurate oil level reading. You will use between 3.2 and 3.4 quarts.
Your final drive uses 80/90 hypoid gear oil. Synthetic hypoid oil will reduce friction and make your final drive run cooler.