[BillW]

I had the standard 3.15 open diff that Backdraft used to supply, they now provide a 3.46 open. I have a 347 Stroker making 410 Horse and a Tremec 5 speed. The speedo is perfect, I checked it against a radar speed notification system in my neighborhood. It works off of a magnetic pickup vice gearing so that spinning part must be a constant (i.e. unchanged) when the gear is changed