I have a 73 F100 that I am almost finished restoring. One of the last parts I need to get is a new rear bumper. I have been looking at the rear bumpers that LMC has for sale but I have a question I hope someone on the forum can help me with. The bumper that LMC sells comes in two variations. One is for bumpers with center mount holes 36 3/8" apart and the other is for bumpers with the center mount holes 40" apart. The problem I am having is neither of these dimensions match anything on the truck. When I measure the distance between the two frame rails I get 38". I also measured the distance between the mounting holes on the original bumper and they don't match any of the dimensions LMC indicate. It originally had the rear step bumper on it but I want to replace it with the more typical bumper like the one here Rear Bumper and Components (lmctruck.com) Any help is appreciated.

Thanks, Robert

 

You should probably measure the mount holes on the bumper brackets as mounted to the frame, or your old bumper.

I know my frame is 37-1/2" outer edge to outer side surfaces. The rear bumper brackets are bolted to these surfaces, they are 37-1/2" apart inside to inside. They are original brackets used with the regular chrome rear bumper, the mount holes for the bumper are in tabs that face outwards from each other. Of the choices you offer ... 40" would be about right center to center ... 36-3/8" would be too close. (I think the one with 36-3/8" bolt centers would likely fit a "highboy" F250, they had narrower frames as I recall). I'll aim to go measure here in a few ... but to illustrate I'll leave this.
It is 40" bumper bolts center to center.



I temporarily added the red cross piece to maybe prevent me or my painter buddy walking into a bracket, only reason for red paint too.

 

I did measure this and it was 38".

 

I went through this process myself. See my build thread. Another member helped me out and I confirmed the information. Highboys and some F-350s had the narrow frame. Yours will be the wider one.

I don’t know where they spec those dimensions from. I couldn’t get a measurement that made any sense to match their numbers either. Get the wider part.

 

The factory widths for 73'-79' for our trucks are F100 - f250 2wd reg cab (37 1/2") , F350 2WD reg cab (33 1/2") , F100 - F150 4WD reg cab (37 1/2") , F250 4WD reg cab 73' - 77 1/2 (40.0"), F250 4WD reg cab 77 1/2 - 79 (37 1/2"), F350 4WD reg cab 79' (33 1/2")

 

Just remeasured my frame (73 F-250 2WD) and it's a bit shy of 37.25. I got my part from NPD and they list the two available widths as 33.5 and 37.5. Obviously there's some variability in the way the various suppliers make their measurements as well as some variability in the frame widths from the factory. Again, I would suggest to you that you get the wider frame width bumper. If you want something that's closer to the measurement you took maybe you should get the part from NPD instead of LMC. I bought the same style bumper from NPD.

https://www.npdlink.com/product/bump...1973&year=1973

This is assuming that you have a 2WD.

 

Of the choices, rwarnoldjr wants the 40" bolt center to bolt center bumper choice.

Reads like you measured inside the frame maybe? Well, it reads like they mean between, but it really means outside to outside of rail. "Between" does typically mean "free space between". They should say:

 

Right. I think that's one of the sources of confusion. It's much closer to 37.5 when I measure the outside of the frame. Still a bit shy of 37.5, but close enough.

 

These bumpers are generic, you just make spacer plates to fill the gap if you have one.

 

The bumper you are wanting to order is normally called a Sport or Contour bumper. And IMO not really good for nothing but looks. No place to attach a trailer ball. No big deal, if you have a drop hitch receiver. Slick to step on, getting out of the truck bed. One bump on the end wings and bam right into the truck bed, under the taillight. Hook a tow strap to it and it folds like a cheap beer can. Some say (rumor has it) LMC "chrome" plating it cheap and thin, so buyer beware. If you get it, you better paint/bed liner the back side to prevent rusting. Just saying.

And the bumper brackets (kit) use to be as rare as gold hens teeth. The NPD bumper does NOT come with or even show an option to order. So the fact that LMC has them is a good sign. Yes you order the 40" bumper, the brackets go on the outside of the frame rails and you make some spacers from bar stock plate metal (or washers) as needed. If you get the other (narrow) one it will have to go on the inside of the frame rails, and I think the cross member aft of the gas tank will be in the way.

Mount the brackets loosely, then mount the bumper.

 

FWIW, I bought a chromed step bumper from LMC and it's crap! The metal is rather thin (as compared to bumpers from the old days), and it started rusting a few weeks after I installed it. After a year, the black paint in the hitch ball platform area was badly rusted. I'm going to keep my eyes open for a vintage silver-painted bumper to refinish and install.