Chuck,
Since you changed the topic to SS brake lines, I'll follow you.
If the seats in your brass fittings/blocks are good, try this: tighten the nut on the brake line until it is snug, Then, loosen the fitting and re-tighten the fitting. Do this a couple of times.
My worst fitting for leaking was/is the fitting on the end of the master cylinder.
Are you using a flare wrench? You will have to torque it down more than a regular brake line (15 ft-lbs, supposedly).
I have read that it is possible to get brass seats to help seal leaks with SS brake lines. I have never seen nor used these seats.
Here's a discussion on sealing SS brake lines. 
