unleaded fuel on older 911s....

The gas stations where I live have stopped selling leaded fuel, which was the fuel I always used for my 73 911. I liked leaded fuel because it acted as a lubricant. Does unleaded fuel afect these older engines? Should I add an aditive? Which octanage should I go for: 93, 95 or 97?
Thanks.

you're lucky to have access to octane like that. i'd go for the good stuff if you can afford it. we're kind of stuck with no leaded fuel around. the hard seats hold up well without the lubricant that the lead provides. they may not last quite as long without it, but what choice do we have? the timing usually can't be advanced as much due to pinging. is the air cleaner after all this?