Hi, Christian -
All that work, and you have found something even better. Or at least more accurate.
You have picked the right location - the road you want is shown as NF-103 on the Bing map,
and the road to Big Horn is the first left off of that one. After you pass the big mountain of
ballast (if it's still there, and not already out along the right-of-way) You'll go up a small hill.
About half way down the other side is a steep, rough road going uphill off to the left. IIRC,
it's marked NF-75. It gets better after the first 100 yards or so, and then real rough again
after you pass the Big Horn wye.
- Russ