I'd like to add a point or two... Which may not upset anyone, but who knows.
The mid 13 guesses may not have been all that far off without the gear swap. 3.42's aren't bad at all imo, but 3.73's combined with the rest of this package might've been the entire difference between 13's and upper 12's. Maybe not .7, but I'm thinking the car may have run 13.3's or 2's without them.
And cool 84... I think rods might make a helpful diff. if they are lighter and or help provide better balance and thus, cause less ... I guess friction would be the word... because of their differences over stock. Rods alone prolly don't do much, but when added to an overall build, I'm of the opinion they can make a difference.
Just observations from what I've read here...