There was no unleaded gas in '69; IIRC, in the USA, unleaded became available in about '73 or '74. What grade of unleaded you need, and whether you need a fuel additive (to make up for the missing lead) is entirely dependent upon what may have been done to the engine over the years. If it has never had the valve seats replaced, you may need an additive. As for which grade of gas you're going to need (octane rating), try it on a short tank of regular. If this makes it "ping" or "knock" under acceleration, you may need to move up a grade. (Or tinker with the engine to make it run on regular, in which case you'll get lot's of advice here on the board. Just be aware that detuning an engine that needs higher octane fuel in order to make it run on regular, usually carries a hidden cost in the form of decreased performance, to include fuel mileage.)

But do try to find out from the previous owner(s) if the engine has had the later valve seats installed, which is the "cure" for lead dependency. And maybe they have already lowered the compression ratio somehow (e.g. thicker head gasket) to alleviate the need for higher octane fuel.

Gary L.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5