^what he said.
And also modern motorsports sells the brace. It took me 6 months to get in contact with ross to accually buy it though... so good luck on that.
An alternative is to swap covers. Put a stock r200 smooth cover on the r200lsd from the 300zx. No modification or brace would be needed. You also need a 280z mustach bar for the 300zx diff if you dont already have one or if you car isnt modified with one. Also you will need the input flanges to each halfshaft and halfshafts from a 280z, or cv shafts from a 280zx(adapter needed that modern motorsports sells) or cv shafts from a 300zx... again adapter needed from modern motorsports.
Cheapest way? Find a 280z in a boneyard and get the mustach bar, diff cover, both halfshafts w/ input flanges(how the half shafter connect to the differential) they snap in and snap out.
Accually I take that back. I have a cover I can sell you. a smooth r200 cover. Hows 35$+shipping?