x2 on the brake fluid (what did you use?). Is the pedal feel harder though with the SS lines installed? What brand are they btw, Goodridge, or ...? And you are sure there's no air in the system?
The pedal feel was VERY firm (and responsive) on my 95 SHO when I upgraded to the Baer Claw pkg with Performance Friction semi-metallics. May have had SS lines on it tho, can't recall.