Jim Tenney posted the route on Turtlehead Peak:
Car to Car. Unsupported, to sign-in book and back.
Starting and ending in Sandstone Quarry turn out off of Red Rock Loop.
This is a very popular route with a big pay off view of Vegas and the surrounding peaks.
I didn’t know this was an FKT, but I spent a lot of time in Vegas one year and remember the time I went for my PR. My goal was to break an hour and I did it! There is a Strava segment for this route and it says my time was 58:50.
There was a group of 30ish men training (all wearing the same clothes) that were over half way down the mountain when I was on my way up, and I caught them just as I was finishing.