Check here for a manual,
http://chevy.oldcarmanualproject.com/index.htm , you should find something close to your truck age.
As for oil, use what you like, the weather in your state is not that much different from other northern areas. If you plan to drive in the middle of winter, then choose thinner oil, but in general, 10 w 30 will work year round. There is really no need for synthetic oil in these old engines, blends are OK, straight weight is also not needed.
Joe
