Been over a year since i took this rear bumper off and can't remember how it came off.
Here is my first try at it but I know this can't be right.
Question is do the mounting brackets stay sandwiched together and bolted to the inside of the frame or..do they split the outside and inside then bolted to the frame? Can't seem to find any info on this.

 

here are some pics of others not '48 though

 

I did my sandwiched together and on the outside of the frame.

 

What does your bumper dictate? I can't imagine the bumper bolt hole lining up correctly if you have the brackets mounted wrong.

 

The first picture you posted is correct..

 

Since not all frames aren't exactly the same I'd say do whatever it takes to line up the bumper holes. I got new brackets from LMC and they were riveted together so I assumed they were not to be split. The only way mine would work was to put them inside the frame...