Farkin geniuses! Should've just replied with "I can't tell you if our brackets will fit because we're jerks."
The st141 may have different caliper mounts so their bracket may not fit. You need the bolt spacing and the distance of the caliper from the centre of the axle. Either that or ask for the dimensions of their ra40 backing plate. Or is that confidential as well!
The other thing you can do is modify and existing pair of ae86 disk caliper brackets to take your tube flange. It's not hard to do.