I guess I'm missing it ... what work?
Nothing needs modified on the case (that's why the cheap dies work), just cutting the neck down to 1.62".
Neal,
You are absolutely correct, "nothing" needs to be modified on the case.
The chamber, however, is a different story.
The 357 Herrett case is 1.765" long.
The "SAAMI" 357 Herrett chamber is nominally 1.780" long.
The 357 Herrett chamber case neck diameter is nominally .385".
A 357 Herrett reamer is going to give you .155" of freebore, on top of the throat that is built into the reamer(usually .075"), that is .028" larger than a .358 projectile at a case length of 1.625".
Using a 180g Hornady SS/SP, loaded to the cannelure - you'll have +/- .200" of grossly oversized freebore/jump to the rifling.
If one is satisifed with shotgun like patterns - using a standard .357 Herrett reamer and an A&B barrel would be the way to get it done.