back of my 86 brat behind the bumper is totally rusted out,. was wondering if i could buy the whole panel whatever it is called, and just weld it in place. it has some contours that would be difficult to duplicate with a piece of sheet metal. plus two recessed areas for access plates where the bumper mounts go through. this seems like it would be hard to fabricate on my own. just wanted to see if there is a full panel that i could buy and use before i start trying to patch it up. thanks.

When I had my Brat repainted 11 years ago I had the same problem. They cut it out and fitted sheetmetal back. It is still intact to this day. So it is doable with sheet metal.

this might help http://www.subarupartsamerica.com/parts/1985/SUBARU/BRAT/GL/?siteid=216122&vehicleid=1267747&diagram=756180

Everything they are showing is discontinued except for #3. Believe you want #6 but it is highly unlikely you will ever find one new.