Correct, It runs down the firewall just before the wire trough as you call it.Thx Chris. My car is a '70 but I believe the T400 is a '66. I see the switch on the drivers side by the shift linkage but it only has 1 blade and the wire in question has two female slots. Should the switch for a '70 have 2 blades?
If this wire goes to the drivers side of the tranny I am thinking it shouldn't run thru the trough on the firewall. I don't think it would be long enough.