Yes, the .38 and .357 cylinders do have a different shape, with the .38 having more "fluting". Didn't know if you had the "blue guns" for the LCR or not, but I'd assume that for the LCRs one would need molds for both models. At least for detail molding of the cylinder, although, and while I'm not well versed in your craft, I'd assume that it would be possible to block it out some way where the cylinder area wasn't detail molded and just had a more cylindrical shape since I assume that the TG area is where the retention takes place... HA! Is that enough assumptions from someone that doesn't know squat!?
Just a thought... Two of my most common EDC guns have been J frames for a number of years (they're just so damn easy to carry!) but I just recently picked up a .38 LCR and have found that I prefer it to my J frames (trigger and sights mainly). Enough so that I'll probably add a .357 version at some point... I only mention that because I'd actually prefer a holster that WASN'T detail molded in the cylinder area so that it could work equally with both calibers.
I can't speak to the .327 cylinder, but I'd assume (yeah, there I go again!) that the .38 and .357 are the most common carry options in the LCR line. Oh, and I have the CT LGs installed as well so a cut to accommodate them would be a good idea too if you ever decide to pursue holsters for these guns...