IIRC, the main difference in thiose two bikes is the WG has the wider fork set up. Frame's the same so the tank should be a perfect fit. Only thing I can think of to check is the stop-to-stop range of motion to be sure the fork won't hit the tank.
If it does look like it will hit, there are fork stops you can buy now to prevent that. In the old days, I drilled and tapped a bolt, then adjusted the extension I needed. Pretty easy as I recall.
The dash mounts are not the same. The tanks will interchange, but you would have to convert over to the appropriate dash. You can see the difference if you really study pictures on eBay. It doesn't appear to be much, but it is different.