As far as 1983, I think it was too early for indexed (other than Positron which I had on a 1979 Suburban, but I think that they faded from the scene before 1983).

I have four Shimano 600 derailleurs, and by their date codes I have been able to estimate that Shimano went to SIS on their 600 line in 1987. The derailleurs with that year's code were labeled as SIS, the previous year was not.

In the late 80's I have bikes from 88 and 89 with down tube shifters. The 88 has Shimano 600 7 speed indexed, the 89 has 6 speed Suntour indexed.

So I think the answer is that if you want to be completely period accurate on your bike, you may need to use friction. However, if you are looking to just stay close, you should be able to find something suitable from the late 80's...