Some so called SS brake lines are only rubber lines with a sleeve to look 'good'. IIRC, you got this from your FIL and he was a real racer. If that's the case I would think he'd avoid that kind of thing. Still, new flex lines are not expensive.
Thinking more about this, rubber lines are good. Maybe they are rubber wrapped with a SS sleeve simply to keep them from being cut by debris from the dirt track. I think you should stop with the bleeding and pull these off and see.
You shouldn't get drain back if there are no leaks.
Besides, you only need them to work for 15 minutes.
