No - 66 and 19 are K-frames. Stainless and blued respectively, the 581/586 and 681/686 are L-frames, fixed and adjustable sighted, blued and stainless respectively. There was nothing wrong with the 19 that was "fixed" by the 66. They did, however suffer top strap flame cutting when subjected to quantities of Magnum 125gr ammo. I have a 4" 66 purchased new in 1982 and it has somewhere north of 130K rounds through it with nothing more that a new cylinder end shake washer at around 70K, probably around 50K of that was magnum loads, mostly 156gr GC SWC and 2400. Few people will shoot a wheelgun enough to wear out even a K-frame.
I think an L-frame. 44 Mag is overdue (though I'd have been happy with a .44 Spec) and has the potential to be a hoot. Especially if fed a diet commensurate with its weight and the tolerance of the shooter. I will have one eventually...