My son, Troy was rearranging his bedroom & asked me if we could make a shelf out of an old truck bumper. We had a small original rear bumper with the mounting brackets from an IH Scout II that fit the wall space almost perfectly. He thought about getting it hung first & then making a wood shelf to top it, but we later decided to top it with steel floor plate so that it look more like a step bumper.
Step 1: Wall Base
A bumper is much heavier than a normal shelf, so it has to be attached securely to the wall. Since the holes on bumper brackets won't fall on the 16" on-center studs in the wall, it's probably best to build a base that will hold the bumper. I used a 2" x 3/16" piece of flat iron. Set your bumper on the base you're creating, trace the location of the bolt holes of the bracket onto the base. Use a 7/16" drill bit to drill holes in the base. Cut the bolt heads off of (4) 3/8"x1" bolts & weld the threaded part from the back of the wall base so that it mounts flush when screwed to the wall. You should mark the studs on your wall (16" on-center in most cases). Hold the wall base to the wall & mark the lines where studs are. Drill two holes on each line. You can now mount the wall base level onto the wall with 3/8"x2-1/2" lag screws. I used a total of (6) lag screws. The above photo shows (5) lag screws. One of the carriage bolt holes matched-up with one of the bumper bracket holes, so I screwed it in later when I mounted the bumper to the wall base. It's best to drill 1/4" pilots holes about 1-1/2" deep for the lag screws.
Step 2: Building the Braces
The floor plate that was available for this project was 14 gauge steel so, to keep it from sagging, (2) braces were needed for the back. You may not need this if you use stiffer material for the top. The material used for the braces was the same as the wall brace, 2"x3/16" flat iron. First, place a straight edge on the top of the bumper & measure the distance from the bottom of the bumper bracket to the top of the bumper to determine how tall to make the braces. Cut the long pieces at that length & the tops at whatever works for you. Place the backs on the bumper bracket & trace the location of the bolt holes. Drill those holes on the long pieces with a 1/2" bit & drill one or two 3/8" holes on the tops before you weld them together. Mount the braces & set them level with the top of the bumper when you bolt the bumper to the wall brace.
Step 3: Making the Top
For the top, it's probably best to build a template out of cardboard. In this project, the deepest spot on the top was 6-3/8" (front of bumper to the wall) & the width was 64" (width of the bumper). I had the local metal shop cut a piece of 14 gauge floor plate to those measurements. The cost was $15. I also cut a piece of cardboard to that dimension. I marked & notched-out the window trim in the back corners (see pics) & traced the profile of the curved bumper onto the template. Use a utility knife to shape the template. Trace the shape unto the floor plate & cut to shape with a grinder & metal cutting disk (or a plasma cutter if you're lucky enough to have one). Use a sanding disk to take off the burrs & blend in the cut lines. Use the template to mark some of the holes on the top of the bumper and the mounting brackets & pre-drill enough holes to mount the top to the bumper. Then use small pan head screws or carriage bolts to attach the top.
Step 4: Other Info
We already had this bumper that we had listed twice on Craigslist for $35. The other materials cost around $20, so the approximate cost to build would have been $55. My son didn't want any of the materials looking new, so we didn't paint anything, excluding the wall plate & the braces which both got a couple of coats of clear acrylic spray in order to keep any rust off of the wall. He intends to add bumper stickers that he finds when we're traveling to load up the bumper part. He's also looking for a cool old license plate to mount on there (from TEXAS off course!).