I owned a '67 122S during George H.W.'s reign. The car was originally equipped with an M40 4-speed manual transmission, and I ended up swapping an overdrive box a few months into my ownership. With overdrive, the old B18B turned 3K rpm at 65 mph, and I believe that its redline was 6K. That gives you a theoretical top speed of 130 mph (208 km/h), but very few motors can touch redline in top gear. The fastest that I ever remember going in that car was an honest 90 mph according to the aftermarket gauge pod I mounted under the dash - the ribbon speedo told me that I was doin' about 105. ;-)

These cars are great as long as you never go faster than 55 mph. Even with an overdrive gearbox, the rear end is just too tall for even spirited interstate cruising. The car will do the job, but it's high-revving, noisy, and it always seemed to encourage the kind of behaviors (e.g. noticeable oil consumption) that convinced me the engine did not 'like' what it was being put through.

How did you get your's (or your friend's) up to 140 mph?