Finally getting an early A-Body
Regarding the re-use of brake lines - it really depends on how your look. I found that with some elbow grease mine cleaned up fine - for the front. The rear line was fairly shot, so I replaced it.
Before you remove the k frame - drill some small holes thru the frame above the k frame bolts. Spray some penetrating oil in there and let it set a day before trying to remove them. You might save yourself some agony or possible damage to the captive nut inside the frame rail.