I got a rear D60 the other day from a guy for cheap. He claimed it was out of an old Dodge, but he didn't know the year. All he said was it had a new posi, and 4.11s in it. How can I tell if this is a 30 spline SF, 35 spline SF, or a 35 Spline FF? What are the external visual clues (without opening the diff) to tell if an axle is a SF or a FF? Also, if you were going to eventually drop a bigblock into your K5, and run at least 38s, would you use this D60, or opt for a D70 or 14bolt? Thanks!