Bone74 said..
Hi
I'm after a fin for old school speed board
US fin box
Did they make weed fins for US boxes
Yes. There are a few, but not the more extreme delta type weed fins. Mainly 40-45 degree raked type.For example: I have a few from Vector, Lessacher, Techtoics. I am sure there are others but you may have trouble finding smaller sizes to suit an 'Old school' speed board.
Bone74 said..
I live in Sydney
Is primbee the best spot for speed sailing
cheers
Probably the closest good place to you, but certainly not the 'best' in Australia.

And it depends a bit on what your definition of 'best' is.