Newbie here -

My father purchased this back in 1979 as a reward for himself. He only used it to go to and from work and occassional short-distance road trips. Here are some other bits of info:

1. Color: Silver
2. Miles: 42,000
3. Original Condition (except radio)
4. Have original documentation (sticker price)
5. 5-Speed

He wants me to sell it, but I'm not sure how to determine a market price. Any help would be appreciated