SR 445 aka Pyramid Highway, as you said is graded dirt/gravel, past Warrior Point where it turns into unmarked Indian Road 2. Its on and off and back on and off the res. You would need to take Sand Pass Rd once you get back on the res, not Indian Road 7, which may be unmarked as well. Indian Road 7 follows the railroad, Sand Pass Rd doesn't.
I've only been about a mile past Warrior Point, while working but I've seen plenty of folks from California driving south so I would guess it's a decent road.
If you can find it where you live, a decent map book is the Nevada Road and Recreation Atlas by Benchmark Maps.
Which ever way you choose, SR 447 or 445, good luck to you, and, have fun.
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