xc 175 83 forks

hi can any one tell me what weight and amount of fork oil i should use on a 83 xc 175 40mm forks? please.

125 wr 1983 = (250 mm) 430 ml oil 15 w front fork 40 mm
175 XC 1983 = (300 mm) 480/500 ml oil 15 w front fork 40 mm

Thanks

15 wt seems a little heavy? I used a 7.5 wt in the wr 250 to give a nice plush ride over the rocks and roots and if I went desert riding, I would go 10 wt. I was only 83Kgs