I'm looking at buying the same guards and noticed a while ago the kits are different.
When i looked into it deeper i found the GSA kit comes with a longer bar end weight to allow for any contact with the standard GSA screen which is bigger. it also seems to have a slightly different handlebar clamp which allows more adjustment to reduce any strain from the extra clearance.
With the GS kit you don't get a new bar end weight or the extra adjustment on the handlebar mount.
I've got a GSA1200 and a GS1250 and the GSA has a 5mm spacer behind the end cap presumably for exactly the same reason above i.e. to provide a little more clearance for the GSA screen. The end bolt on the two though is exactly the same size so the spacer makes no difference to tightening it down.
So i would say yes the GSA kit would fit, as its exactly the same handlebars but you may, or may not, need to use the wider GSA weight. With the GS kit you just re use the standard weight. It will all depend on the handlebar mount that comes with the GSA kit and the adjustment it permits. They also mention that you may have to slightly adjust the lever perches slightly to allow for extra clearance the GSA screen may need which isn't needed if you have the smaller GS screen.
I'm looking to buy in the new year for the GS and i'll be going for the GSA kit. If i need to fit the wider bar end weight its not a biggie and doesn't bother me in the slightest.
Hope that helps,