This sounds like a common dent that occurred like most: the gun fell over or was swung against a corner of something.
Locate a competent gunsmith that has experience with old doubles. Get him to look it over and give his assessment. Post some pictures here and get the crowd's assessment. You'll get everything from "...I'd never fire that gun again" to "It'll be stronger thene"
With regard to longitudinal vz. radial, I'd say your dent is the better of the two. Hoop stresses are higher than longitudinal stresses.
Barrel steel in general is very mallable. It is less prone to cracking than most would believe. If you look at many high grade guns and high grade LC Smiths, you find many examples of heavy engraving right over the chamber. These engravings have very sharp cornered cuts and are about as perfect a stress riser as you could manufacture. Yet, when have you heard of a chamber failing on one of these engraved guns?
