Dave,
I don't think I would break up a matching original for parts to go on that other shell. The .38 looks pretty good as is, and has its own value that should be considered, while the Pacific (or whatever it was) shell is pretty rough and not likely to ever have any great value as a shooter... if the original .38 can't be fixed to suit you, it would be financially better, IMHO, to sell it as is and complete and use new parts, if nothing else, to rebuild what is not and never again can be an original rifle. This is JMHO, of course and worth what you paid for it, but you did ask!
Froggie
PS Since the .38 is a forged action, what would keep you from making a heavy barrel for it and then you could stock it as desired and you would HAVE your .45-70 (or whatever caliber desired) Pacific-style Ballard and not have to "break up" the parts that are numbered together? Just a thought.
