There is probably a gunsmith somewhere that would attempt it. Moon clips are for rimless rounds, a better question would be a source for rimless .357 magnum rounds.
I can't think of any reason why cutting the cylinder on a Ruger would be substantially different than cutting it on a Taurus. Some gunsmiths are leery about working on unfamiliar guns, but if you explain to them that you will not hold them responsible if they do mess up the cylinder (expensive, but replaceable), they may agree to.
Also, actually finding the clips may be tricky as well.
Where in the heck are you getting moon clips for a 7-rd .357 set-up that will fit your 66? By the time you get done doing all that (and totally voiding the life-time warranty on your Taurus) you will discover that buying speed loaders would have been WAY cheaper.