All K frame barrels are threaded the same .540x36 (except the very early 1896 models). A barrel for a pinned frame will work perfectly in an un pinned frame as the pin actually does nothing on a correctly fitted barrel. In fact an un pinned barrel only takes a couple file swipes to have a slot for the pin. But, the catch is the profile of the top of the frame where it meets the barrel and the barrels top profile. Model 19,14 and 14 barrels with sight ribs will not match at the rib on fix sight frames, unless you mill in and add a sight on frame. Heavy fix sight barrels will have a tiny protruding corner on each side when stuck on a regular frame etc.
I have bought 7 of the J&G 10-7 frames and made them into 9mms, 357s, 327s, and 38s. They all came out well with some work. I had a lot of fun. Oh, also the J&G guns are re imports and as such have some stamping under they yoke pivot. This can be removed (legally, I contacted BATF). I first tapped the stampings lightly with a 40z hammer then sanded smooth. I will reblue the whole lot at some point.
A completely reworked model 10-7 frame into an adjustable sight 327.
a 10-7 frame fit with a Colt Python barrel and recessed 357 cylinder
Look closely and you can see where import stamps were removed under yoke
this one has a nickel model 19 recessed 357 cylinder and a nickle model 13 barrel
Finding just cheap frames is difficult. I have a 6" Nickel Python Barrel looking for a home. I bought a nickel model 15 with a messed up front sight to put it on, but it was to easy to fix the sight and hard to molest a nice gun once repaired.