If you intend to bolt the shock mount to the outside of the 3/16" thick tubing, you either need to open up the holes on the back side so you can run the lock nut in to the back side of the outer wall (I believe that single wall 3/16" thick steel would support the shock function). The back side would just have larger holes. You may have to remove the grille should you ever need access to the nuts.
If you are bolting through both sides of the tubing, in order to keep the tubing from crushing, you are going to need some sort of spacer over the bolts with a heavy duty washer under the nut. I believe that if you just pass the bolts through the tubing for the shock/light mount, the shock function will keep pulling the inside tubing inward and the bolts will always be loose. The nut, washer, and spacers might create clearance issues with the grille.
I don't know how you would put a bung on the inside of the tubing without cutting a piece out of the inside (or outside) wall, but that would work just like the nut against the inside of the tubing wall. that would not interfere with the grille clearance.
Another option might be a threaded insert from the back side of the tubing, but I don't know how that would effect the clearance of the grille shell.
Since the frame is unfinished at this point, another option might be to cut a part of of the outer wall, then drill your holes through a 1/4" plate with the nuts or bungs welded on the inside that match up with mounting bracket for the shock/light holder, and weld the 1/4" piece onto the outside of the frame rail tubing. If that 1/4" plate reached both the top and the bottom of the side of the tubing, it would support the shock action easily enough. To me, this would be the best option, after enlarging the holes in the back side and running the nuts up against the outer wall of the tubing.
The headlight will likely not be the issue, but the shocks will cause a load on the setup.
Hi Gene, Guys.... Revisiting this again. I'd like to start messing with this today.
This is what I'm thinking, sort of a twist on one of your idea's Gene. I have 2 needs, no nuts or washers on the inside of the frame rail, and a solution so I don't crush the tubing and end up with loose bolting all the time.
I don't have enough room at all 3 because the lower bolt is to close to the lower section of the box tubing and I'm sure that area will be self sufficient. However the top 2 bolts are close to center of the tubing which will be easiest to crush if it's going to happen.
I think the bolts are 7/16 ...not in the garage right now.
So I take a nut and cut chamfer on the outside edge to accept a flush weld, on the backside I cut a step in OD of the Nut that would accept a 2" long piece of steel tubing that has a 1/2" or better ID. Weld that tubing to the backside of the nut.
I make the hole on the inside of the rail large enough to accept this nut/tube piece and I fit the length so the end hits the inside wall of the tube while the face of the nut is flush. Put it in place, bolt it up so I know I'm lined up, and weld er up and grind it flat. It doesn't have to be perfectly flat, could be slightly mounded cause it is hidden by the grill. I just can't have the nuts interfering with the grill.
Whadauthink?