For the record, here is the current Highway Posting on 105 - and it's pretty clearly not the speed limit.
And a view that the friends of Janis Hendrickson might have seen while trying to break the land speed record back in the '60s.
If you look closely it says "55" not too far down the road. The speed limit, that is, not the highway number.
Is it just me, or did this highway seem to be a lot wider when it was first built?