The significant differences among N-frame revolvers are:
1. Cylinders. Three different lengths, different capacities, fluted & unfluted.
2. Sights. Fixed or adjustable. Front sight height varies by caliber.
3. Barrels. Length and profile, exposed ejector rod or underlug, multiple underlug profiles.
Note that different cylinder lengths can result in different overall lengths with the same barrel length (a .45ACP short cylinder with 4" barrel will be about 1/8" shorter than a .357/.41/.44/.45LC revolver with 4" barrel.
Both the 627 and 629 use the same cylinder length. Both have adjustable sights. That will leave barrel lengths and profiles, and cylinder capacity/fluted vs. unfluted.
Most production holsters from the larger manufacturers will be made to accept just about any of the possible variations, with forming to accomodate.
Hand-made and formed holsters may not accept all variations, as they are specifically formed to the intended revolver. Examples: (1) a holster specifically formed for the 625 in .45ACP with standard barrel profile and underlug would be unlikely to accept a 627 or 629, particularly if equipped with full-length underlug; (2) a holster specifically formed for the 6-round .44 magnum cylinder would be unlikely to accept the unfluted cylinders or 8-round .357 cylinders.
In the shop I use 3 dummy guns and 4 actual revolvers to duplicate most variations. There are still some N-frames that I cannot do.
