There's no reason to replace that Unilite distributor, it is great. Just add a Mallory HyFire VI A with it. I'd still have mine in the Chevelle if the advance stop hadn't broke. Mine was about 15 years old before it broke. They are also easy to adjust. You use springs to adjust the advance curve and the timing tab to adjust the amount of total advance. I'm not sure what works for a BBF but I would set initial timing at 14 degrees with a total advance between 34-36 degrees all in by 3000 rpms.
http://www.summitracing.com/parts/maa-6852m/overview/