I think its time to calm down on 75mph 2 strokes, they are not that common. My gpr was pushed pretty hard with mods and 72-73 was about it with my 175 on it and it was usually 70-71. My daughter hit 74.1 once in perfect conditions but couldn't repeat it.
There are a LOT of guys that say their 2 stroke did 75, and most of them were full of BS.
Setting GP conversions aside, getting to and crossing the 75 barrier is nothing to sneeze at, although certainly its much easier than it was back in the day since we have other people's work to copy but there is still some serious expense involved. 70 really doesn't take much but 75? that takes some effort and each mile or two after that requires deep pockets.
I've ridden with some seriously fast ski's 85+ and not a single one said "boy, that was cheaper than expected"