Don't do 747's. The routes won't give much because of the high fuel consumption, and the price will kill your maintenance. Although, you've reached a size where one or two wouldn't make harm - just make sure it is the fist thing you get rid of when you get in trouble.
Other than the Il-62, you can use the 707, Il-76, Tristar or Tupolev 114.
Out of those (and my memory of the data) I would choose the Tristar for the speed, Tu-114 for economics, Il-62 for the range and 707 for a good-for-all plane.
Please note that I am not in any 70's world, so I don't have access to exact data.
I hope this helped
