Gary, not meaning to argue back -- there's a fair amount of gray area in this topic.

The owner's manual for our '66 122S specifies both 6.00-15 and 165 S 15 tires, so I would think radials were at least an option, unless that only applied to non-U.S. markets. I didn't come upon Volvos until '78, by which time radials were the common thing, so I really don't know.

I have a customer who took delivery of his 122S wagon from the factory in Sweden, and he had a heckuva time convincing them to put radials on it. They made him sign a bunch of waivers and disclaimers, so I know for sure radials were not standard on the wagons. (There was nothing he could do to convince them to put an OD trans in it.)

The aerodynamics thing I got from an article by Pete Brock (of Sting Ray, Cobra Daytona and BRE Datsun fame) in Classic Motorsports magazine. Can't tell you exactly what issue, but he went on about it at some length.

The contact patch thing came from HERE. Don't know how authoritative that is, but it made sense to me.