77 KZ1000 stock to modern fork swap

I'm not certain, but I'd wager the stock top clamp on the zx9 is some type of 6000 series aluminum you should be able to gullwing it with a spacer and get it weld it up. Then of course it would need heat treated.

I know one person who gained his clearance by welding up a flat collector instead

May not work but what about a 19" front wheel and spaced fender to match?
Steve

Ramtough did the 19" wheel with the help of either leon or les. Details are in his build thread.

But there isn't much 'modern' tread choices with a 19.