6.901 is the OAL of a stock 5.9 magnum pushrod. Seems every manufacturer has their own way of measuring. Have you done anything that needs a different length pushrod? Milled heads/block, small base circle cam, thin head gaskets? And are you measuring to get your length?
Reground cam. Thicker head gaskets. I measured the base circle of the cam and it was smaller than stock but I lost my note on the measurement.
I made a homemade push rod length checker and kind of tried to get in about the top 1/2 of the lifter travel.
