Vikings: Nordic Roleplaying for RuneQuest (1985)

From the text:

Vikings is a combination of both fact and extrapolated information... It includes facts from all known literary records and interpretations of those facts, run side by side despite the anachronisms.

The historical Viking Period roughly occurred during the years 780-1070 AD. During this era, hundreds of younger sons left home in search of land, fame, and wealth. They pillaged and settled in kingdoms from the Mediterranean to Vinland. This era could form the basis for a more or less historical game, enhance by the fantasy elements and whatever anachronisms the gamemaster desires.

Alternately, the legendary era may be used. Less is known about these years, save for the tales set forth by Saxo Grammaticus and Snorri Sturlasson. The favored period would be 500-575 AD, the time of Beowulf and Hrolf Kraki. In those days the gods still strode the world and mingled with men, monsters roamed the earth, and the Scandinavians knew next to nothing of the outside world.