To clarify:
The models 10 and 64 are both chambered in .38 special, with the only difference being that the model 10 is blue or nickel, and the 64 is stainless.
The models 13 and 65 are both chambered in .357 Magnum, with the only difference being that the model 13 is blue or nickel, and the 65 is stainless.
The S&W models 10, 13, 64, and 65 are all built on the K frame. The only difference between the models 10/64 and the models 13/65 is that the models 10 and 64 are chambered in .38 special, while the models 13 and 65 are chambered in .357 Magnum with a slightly longer cylinder to accomodate the longer .357 Magnum cartridge.
To muddy the waters a bit, there are a FEW model 10-6s and a FEW model 64-1s that are chambered in .357 Magnum that were prototypes that eventually became the models 13 and 65.
Without looking closely, all of these guns will look and feel pretty much the same. All will fit in the same holsters.
I hope that helps.