First, is the seat adjusted all the way up*? It may interfere with room between his thighs and the bottom of the steering wheel, but if he has skinny legs it will give him a couple of more inches.
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* New owners of 240s often don't know that the drivers seat can be raised and lowered. There's a lever in the front to adjust the seat's front height, and a separate lever in the rear of the seat to adjust the rear height (being independent adjustments, they can also be used to adjust the seat's tilt).
BTW, the passenger seat also adjusts, but rather than easily with release levers, for this you have to remove and change the positions of 4 bolts, each at the corner of the seat.
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Second, once when I bought an '84 240, I was wondering why the seat went so far back -- much farther than any other 240 I had owned (or have owned since). It was very peculiar, so I unbolted the seat and discovered that between the seat and its regular mount there was a second mount that repositioned the seat about 3 inches rearward -- in other words, this device relocated the seat relative to its usual mount. I threw it away (not needing it), but it appeared to be commercially made, as if it was a dealer-installed Volvo item to help tall customers better fit in their new car.
Thus, you might ask your dealer's parts counter if they can find the item and order it for you.

Good luck.