The 0.85" bars are the most common OE size in the '70's cars. If you demand new ones you might be out of luck as it's not a 'performance' size in any sense. After exceeding the yield stress in an 0.83" bar on my drag car I use the '85's now.

I run the /6 Bars in my 68 Barracuda and they work well. I drive it lots on the street and they handle OK. My car is also a little more nose heavy than most, it has W2 heads on an R1 block as well as the stock steel hood.