Hey guys i know people post alot of stuff about N/A B series but everyone is auto.

My question is what diff ratio should I get for my 5 speed MANUAL xr6? I do alot of highway driving so 4:11 is out of the question, thinking 3.7 or 3.9

also will a diff out of a xr6t just bolt up to my N/A? Because they seem to have more options as far as LSD's and whatever out there for them.

I would personally not go beyond 3.7s in any manual falcon.
The xr6t diff will fit in and you will need the constant velocity shafts with it though im unsure if the diff cradle or tail shaft is the same.