Is that Harken track on the front beam? I had a 6.0 about that same age with a self tacking jib that used a foil instead of bridal wires and a single block & cleat for sheeting.
It doesn't look like a 5.8. The rear end of the hulls are finished. 5.8 were not.
An even older version used bridal wires up front like a 5.8