Hi Tim,
There are four steel types for OM Rugers:
1. 4" Earliest with long dog leg cutout slot
2. 4" Short dog leg slot
3. 4" straight slot with large screw hole for stud on the barrel (same as New model)
4. 4" straight slot w/standard size screw hole, no stud on barrel (same as New model)
Tell me which old model it's for and year it was made if you know or serial #, then I can tell you which you need with part number if it's one still made.
For the 357 Max you need a 5" Ruger number 90179, Brownell's #780-001-198. Do you have the longer rod and spring?