13.7" pin and weld ASR brake question

That version says in the description... and provided you saw the .30 cal part, I would think you would be GTG.

AC5364 uses a longer rear shank for pin and weld applications on 13.7" barrels to meet 16" overall length.

It appears to be made for pin and weld, 13.7" or longer .... in the advertisement.
So thread it on and measure the length from bolt face to muzzle end, it must be slightly over 16"....one could add a sold bushing to make up a little difference if it was barely under....but it should be fine, if your barrel is at least 13.7". You are responsible for measuring it correctly....so ya don't have a SBR , without the stamp.