Those are mighty handsome.
If your 340 fits, they'd be a bit long on a pre-Model of 1953 I or J frame.
Since you don't have anything period-correct to put them on I'll send along my address and relieve you of the burden of finding something that would be.
They'd look great on this 1954 Chiefs.
Bob
ps: Hmmm. Now that I look closer, they might have originally been made for an older I-frame or a Baby Chiefs. It looks like somebody Dremeled them for a newer one.