I found a previous post about a pre-96 357 Survivor with nickel frame, if it's an SB2 frame and made before '99, you'll be limited to low pressure chamberings, those marked with an * on the accessory barrel list. The best way to find out what can be fitted is to call H&R and give them the serial number, they'll tell you. toll free (866)776-9292, you can email them too hr1871@hr1871.com
I wouldn't worry about the forend fit, all forends have the same channel with the exception of the 10g/12ga USH, all barrels are about the same size where the forend fits with the exception of the Superlights, the taper is just different.
Tim