The XKR 175 appears to me to have the speed pack or its equivalent. Like the Speed Pack, the XKR 175 is lowered a bit I think, has the deeper splitter, deeper rear diffuser, aero bits on the side sills, the larger rear spoiler, the speed limiter ceiling boosted to 174 MPH, and the transmission mapping altered as required to get to 174 MPH.

But yes the 75 is different than the 175, and better. My understanding is that the 75 added 20 Horsepower, a different exhaust system, a stronger torque converter, and different (possibly wider) wheels. I wonder why those bits didn't make it to the US?

 

Yes, that's the Speed Pack. The 75 also has what later became the Dynamic Pack, with 30% stiffer suspension and modified uprights for better handling, and the 10.5" rear wheels. Plus it has the Performance Active Exhaust and the extra HP. As an added bonus, I found mine is limited to 186, not 174. So, it's basically an R-S, less a few HP and the R-S styling, which I don't like (and it only adds 1% downforce)

I'm not sure why they didn't bring the 75 to the US - perhaps because it was a limited run of 75 cars, to commemorate the 75th anniversary, and those all sold pretty quickly. I think they introduced the 175 as a consolation.

 

What does the R stand for? My wife asked me that yesterday. All I could come up with was Really cool...

 

Horsepower. Engine gets supercharged. More goodies.