Although I'm admittedly a noobie here, I do have experience with "outsourced" or non-original spoke kits for vintage bikes. My advice is to not do it- the temptation is there because they're cheap, but something always seems to be lost in translation. Bends can be just different enough as to not fit correctly, threading differences, lengths, thicknesses, metal strength, etc. are all variables. You'd think spokes would be simple, but in reality they're not and you're better off holding out for original Yamaha parts, or re-plating (clear zinc) your originals in the off season. You'll avoid much frustration this way!