Are you making a cyl? Or if you're starting with a 357 cyl to ream, it will not reach the barrel forcing cone so the barrel will have to be set back. And it will be a bit short for 44 Mag cartridges with longer bullets.
You may want to consider reaming the longer 41 Mag cyl.
Reworking an original 357. Here are pics. These make a very, very efficient and accurate way to re chamber. Manson discontinued these as in stock tooling. Now have an 8-10 week production time and are special order.
There's lotsa 44 Mag cyls to be found, both fluted and non-fluted. Of course you'll want to know the throat diameter and might have to ream them for uniformity. Are the throat cutters still up to size on your old Manson reamers?
They'll fit your 357 if it's a large frame, just have to trim barrel for their length.