I seriously doubt its a Mountain Rifle if it dates to the early 1980's as I am about 95% certain they did not produce those until around 1986 or so. If it has the mountain rifle stock and barrel profile odds are its not factory and just something someone put together.
From History of the Remington 700
1986: Remington rolls out the slimmed down, lightweight, compact Model 700 Mountain Rifle with 22-inch barrel. Touted as the ultimate mountain hunter’s rifle, this shorter, lighter 700 quickly became popular with deer hunters everywhere.