The Taurus M608 is built on the large pistol frame, approx. the same size as the S&W N-frame. (The same frame is used for a .44 Magnum.) There is no way you could get eight .357 Magnum rounds into a K-frame size cylinder. That's why the smaller Taurus M66 only holds seven. Your cylinder is approx. 44mm long compared to the M66's 40mm. That makes for some interesting load possibilities.
By the way, the fixed-sight 3" barrel M608 is a pretty rare animal.