You will have parallax problems at under 100 yards with most center fire rifle scopes. That's generally not an issue when hunting, the error is usually well under 2 inches. For precision shooting at ranges under 100 yards it's best to have an adjustable objective scope. I use a 6x fixed power scope on my 243, 250 Savage, and 7mm-08 hunting rifles. I have a 2-7x scope on my .223 527 carbine and a 4x fixed power on my 7.62x39.
Depending on brand and condition, 40 years old means very little or that scope isn't worth using.