What brand,type etc base should I put on a Mdl. 57-3 Smith&Wesson , 41 Rem. Mag. ? For a red dot site.

Tuck2, not sure which base you need, but I would look for a Weaver type. You have to make sure it is long enough for the red dot to fit as most of these scopes have a long turret in the center. Most will not fit between a Burris LU type base and rings unless you get an extension ring. Millet makes a scope that will fit between the rings on a short base but I didn't like it because I had to turn the light almost all the way up to see it outside. I will look in my books to see if I can find one.

For a mount try Weigand

I'm not sure if your revolver came drilled and tapped from the factory, if not I think you will need a gunsmith to install the mount properly. To check, remove the rear sight, there should be three holes drilled and tapped in the top-strap, if there are only two then more holes will need to be drilled for the mount.

Weaver base #401 fits K,L & N frame S&W revolvers.

i have had several types of bases on my s& w revolvers ,weaver,eveloution gun works ,weigand
my choice would be the latter 2 as they give you greater scope mounting flexability in other words more cross slots in the base. the weigand will put the scope closer to the bore of the gun
as it surrounds the top strap and the others mount on top of the top strap. bobthenailer

I have an Aimpoint ( weaver style )with base and rings for 57 that does not have the 3 mounting holes. Also a Buehler set of base and rings for taped ( 3 mounting holes)-stainless. can sent pics if interested.