The .38 Long Colt was once used by the U.S. military and is the parent to the .38 S&W special. It is basically the same except it is shorter than the special.

Old brass and old data would be somewhat different than new brass and data and the two should not be mixed unless the loader knows and understands the differences. Brass can be made from .38 special brass by simply trimming it to length. Data should be plentiful, at least for lead bullets, from most powder suppliers/manufacturers in their "cowboy" data areas.

My biggest concern in this area would be the age of the firearm being used and would it be safe, or advisable, to shoot it with smokeless powders? Either way, I'd stick to the lowest charges to keep pressures down.