I need some advise. I'm looking at a 3953 3rd gen Smith. Can it be converted to a DA/SA like a 3906 smith has? I'd like a 3906 but cannot find one & the 3953 seems cheaper & more plentiful.
Jbethel is correct. They are a different animal as signified by the different slide, different hammer, and configuration of the firing pin retainer. The slide is not machined to accept the safety/decocker of the 39xx TDA guns.
The railed TSW guns were designed from the outset to use as many TDA parts as possible to make them less expensive to produce.
Regarding the substitution of one pistol because you cannot find what you seek... the 3953 is an alloy frame single stack compact and the 3906 is a steel frame full-size.
A DA/SA substitute for a 3953 is a 3913.
The closest model to a 3906 would be a 2nd Gen 639.
There is also a 3904 which is an alloy frame black version of a 3906 and the Value Line 909 which is similar to the 3904.
The 3906 is definitely a scarce pistol, not easy to find. The 639 isn’t exactly the same but it is close, and they made many more of the 639. It should be much easier to find.
There is nothing wrong with a S&W 3953 that ammo and trigger time won’t cure. Once a shooter becomes familiar with the trigger system speed and accuracy are not a problem.
If you find yourself on the northeast side of Atlanta contact me; I will let you shoot mine.