Well, you know how to rebuild a bike and know what is involved in keeping an old girl on the road. The Hawk will have a much more limited parts supply than the older nighhawk did however.
Personally, the SV650 is the newer, “better” bike. But he Hawk holds a special emotional appeal. The GS is a purely practical descision.
I’d ride both the Hawk and the SV and then decide which you liked better. If the Hawk feels better, does it feel good enough to justify all the extra work and money it wil involve? Really, the SV650 is the closest we have to a successor of the original Hawk.
“The two seconds between ‘Oh S**!’ and the crash isn’t a lot of practice time.”