I'm looking to see what the ideal street slick to run on a 15x10 5.5 bs on a 70 chevelle
i was looking at a 26x11.5x15 mickey street et
but any input would help, graemlins/beers.gif

Unless it's a gearing consideration with your car and setup, I'd run a 28" tall tire.
Makes a larger footprint...greater contact area.
An 11.5" width will fit fine.
Actually a 12.5" should work too.