I ran the green Redline brand synthetic gear oil in my last S/P car with a used set of stock Dana 4:56 gears and M.W. 40 spline spool and axles, lots of runs with no issues, that car weighed 2850 Lbs. with me in it and would 60 ft, in the low 1.20 off of the trans brake glide tranny
That car had a blown B1 motor and drivetrain that had 6.17 gears in that Dana 60 with the Redline Green synthetic gear oil and those gears look great when I changed them