And here is a study i found, testing different clubs from different eras.
Click on link at bottom to see all data.
Macgregor persimmon 1949
Average distance of test subjects-224.7
Taylormade R9 2009
Average distance of test subjects- 246.7
Increase of 9.8%
Assuming no increase in technology from 1949 to 1968(lol), the 68 Tour players would be expected to average 279.9 yards(their 255 average*1.098). Actual 2009 PGA average was 287.8 so the old timers would still average 2.8% less than 2009s players.
But, of course there were technological advances between 1949 and 1968, and as such the numbers from 1968 shouldn't increase by the full 9.8% increase we saw from 49 to 09. Just how much to discount the advances is tough to decipher.
Just for fun lets say that only 75% of the increase can be credited to between 68 and 2009. That would mean 68 distances would increase by 7.35%(9.8*.75). Now we get that 1968 guys with 2009 drivers would average 273.7 yards. Over 5% less than the actual 287.8 average.
This argument is for the most part hilarious. It's obvious to anyone with half a brain that today's golfers are stronger, bigger, and more athletic and therefore will hit the ball further than eras past no matter what you put in their hands.