We just explored this mountain this weekend with my friend on a stock Wrangler Unlimited X (9.7'' clearance with 17'' wheels).
I must say, this was a bit stupid of us, because we had a stock car with no winch and little experience. But it was a hell of a lot of fun
Nevertheless, it appears that this trail is possible to make on a stock Wrangler (so, I guess, a stock FJ should not have a problem either). If you drive past Pearce on Ghost Town trail which turns into Pearce rd, heading south you will see what looks like an abandoned mine road on the left (here's the google maps link: maps.google.com/maps?f...t=p&z=15).
We entered the mountain here: maps.google.com/maps?f...&t=h&z=17,
although a better road is probably the first wash after W Humphries rd, which is where we exited. And got up to here: maps.google.com/maps?f...3&t=h&z=18
We did not get all the way to the top, as it got too rough and it was not clear if we would be able to turn around. Most of the road has a lot of vegetaion and tall bushes that grow right in the middle of the road. Some parts are severely washed out and we had one tire stuck in a ditch at one point. I'd say it is a moderate kind of trail where you would definitely need two people and high clearance. Watch out for the soft edge.
I've attached a google sat image and a sat file for TomTom GPS. You can use the two to make a map overlay for TomTom.