I've just purchased a 68 tripower vert. that has been sitting on a slab for approx. 25 years.All original paint and interior. Under side of car is "very rusty-surface only"

The only way to properly replace the brake line(s) is to remove the body.
You can cut/splice them, but...not really a good idea on brake lines...it's a safety issue.
The brake lines do run thru the frame at the rear "kick-up" area, by the rear wheels, which makes it a bit hard to do with the body on the frame.
The fuel lines can be cut/spliced(w/compression unions) with no ill effects, to get them installed without pulling the body off the frame.

If you are replacing the calipers, go with the "o-ring" style. You'll be much happier in the long run. Check with any of the Supporting Vendors here for those.
Stainless fuel/brake lines are neat to have, but hard to work with. They don't bend very easily if you need to "tweek" them. Adams' Apple2007-02-18 12:49:29

Lonestar Calipers is who I used.  Got the calipers (stainless steel type) for around $80 each about two years ago. 

I also put in the braided stainless steel lines in place of the rubber ones.  If that car has set for 25yrs, then when you try to take the rubber lines off (and you need to take them off) you will most likely have a galled fitting.  Take your time and use something like PB Blaster to soak the fittings (both ends), work the fittings back and forth and make SURE you have a SOLID WRENCH on the steel line side. 

Take it from me, it is VERY EASY to twist off the ends of the steel lines and then you get the pleasure of learning how to remove the lines.

As Joel said, you can use flare fittings on the fuel line but it is a safety issue to try and splice the brake lines.

Good luck!