Also need to replace some of the rigid brake lines. Is it an acceptable practice to use compression fittings to connect lines, or must they have double flared fittings at all termination points? I'm setting this car up for car club track use. Will the scrutineers frown on this? TIA for the help.

The reason for the large plug gap is because now you have much more "juice" to jump the gap which will result in better combustion and longer plug life. A larger spark gap will have no effect on hitting valves.

As far as the brake lines go don't take any short cuts. If you don't have a flaring tool, beg, borrow, or buy one to do a double flare. Better yet, go out and buy new lines if the old ones are no good.