On exterior work I prefer metal boxes. You need to locate a stud onto which you can affix the box. Depending on the type of fixture you may need a hexagonal box. There are usually holes in the side of metal boxes that you can use to drive screws through to affix the box to the stud. You need to use one of the knock-outs for the romex and use a romex connector to protect the romex and hold it in place. You will also need to bond the ground wire to the box using a ground screw driven into one of the holes on the back of the box.

RenoRooki, it seems that you have it pretty figured out. You're right about finding a joist to hang the chandelier from. There must be a reason the box is where it is. If you're going to find a joist to hang the chandelier from any junction box will do, but if you're using the box make sure its correctly rated to avoid having to re-do the ceiling AND get a new chandelier. Then you may have to move it anyways. Colby has a video explaining the process of hanging chandeliers. I hope it helps! Here is a link that might be useful: Del Mar Fans & Lighting-How to Hang a Chandelier

Well...only two things I see can be done. Screw the fixtures hardware into the masonry as high as you can but still covering the electrical box. Or Find or manufacture a medallion with a hollow back that will increase your mounting area. Hope you comprehend what I'm trying to say

Thanks. I think I'm going with mounting the crossbar direct to the masonry. Maybe over the existing box, maybe above or below since the base of the fixture is vertically elongated and will cover the existing outlet box. I have not mounted anything in brick in many years, long enough ago that I probably didn't do it right. It is best to drill into the brick? Is it acceptable or perhaps better to drill into the mortar? I'll probably just grab some tapcon anchors but haven't used them before that I recall.