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**71CHEVYSHORTBED402** · 03-11-2019, 11:25 PM

I think it's finally clicked, thanks to input and research. I'm basically SOL.....................Just kidding, but if anyone has nice set of OEM rear sport bumper brackets off a 2WD, SWB with leaf springs, please PM....At any rate, here it goes.

A. If they remake a working set of rear bumper brackets for a 2WD, SWB with leaf springs then it's probably an accident. Makes me wonder if earlier years might work, when did they begin installing rear coil springs?

B. I'm 99% certain my bumper bolt pattern of 5.3/10” is factory intended. On most trucks the rear bolt hole is approx. 1.3/8” from the rear of the frame. That doesn’t work on a 2WD SWB with leaf spring frame, and you can see why by the picture under post #3. That’s why the hole is 8/10” from the rear on my frame. That and the forward-most hole is centered with the shackle bracket. The bolt pattern is 5" on most other trucks. Can't speak for 4x4.

C. They probably punched the holes in 10ths. That’s consistent with the rest of the exterior; it was all assembled in 10ths, or at least most. Not sure about the front bumper, but it is likely the same. Past experience 10ths can be confusing, it had to be explained to me. Inches are still inches, it’s just broken down into 10 parts of an inch instead of eight parts.

D. Next time someone says “all outer brackets are the same” you can edgeucate. If I were to use the common brackets the bumper would set approx ½” further back than specs. Now I know why my bumper looked different when it was on using old 4x4 brackets. Irony is a lot of vendors use “my” part number to sell common OER brackets. They should be referencing 3892477-78 for the outer brackets.

E. There’s an option to use common “coil spring” brackets for my application, but the inner brackets have to be fabricated for a front hole to match the frame. Again, if these are used the bumper will sit approx. ½” further back than specs. The “4x4” brackets can be fabricated to work as well, with the same result………….

There may be an option to use the front hole on a coil spring inner bracket, and fabricate a new hole on both the inner and outer brackets for the rear hole. Guess what, that puts the bumper where it’s supposed to be or close enough. But might that change the pitch? If that works the new holes would have to be nuts for flush bumper mounts. The more I think about this option the more I like it, but OEM correct would be awesome.

F. Wish I’d bought a coil spring truck……….HA!.Thanks for the help

03-11-2019, 11:25 PM	#10
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,120	Re: Rear Bumper Bolt Pattern Thread I think it's finally clicked, thanks to input and research. I'm basically SOL.....................Just kidding, but if anyone has nice set of OEM rear sport bumper brackets off a 2WD, SWB with leaf springs, please PM....At any rate, here it goes. A. If they remake a working set of rear bumper brackets for a 2WD, SWB with leaf springs then it's probably an accident. Makes me wonder if earlier years might work, when did they begin installing rear coil springs? B. I'm 99% certain my bumper bolt pattern of 5.3/10” is factory intended. On most trucks the rear bolt hole is approx. 1.3/8” from the rear of the frame. That doesn’t work on a 2WD SWB with leaf spring frame, and you can see why by the picture under post #3. That’s why the hole is 8/10” from the rear on my frame. That and the forward-most hole is centered with the shackle bracket. The bolt pattern is 5" on most other trucks. Can't speak for 4x4. C. They probably punched the holes in 10ths. That’s consistent with the rest of the exterior; it was all assembled in 10ths, or at least most. Not sure about the front bumper, but it is likely the same. Past experience 10ths can be confusing, it had to be explained to me. Inches are still inches, it’s just broken down into 10 parts of an inch instead of eight parts. D. Next time someone says “all outer brackets are the same” you can edgeucate. If I were to use the common brackets the bumper would set approx ½” further back than specs. Now I know why my bumper looked different when it was on using old 4x4 brackets. Irony is a lot of vendors use “my” part number to sell common OER brackets. They should be referencing 3892477-78 for the outer brackets. E. There’s an option to use common “coil spring” brackets for my application, but the inner brackets have to be fabricated for a front hole to match the frame. Again, if these are used the bumper will sit approx. ½” further back than specs. The “4x4” brackets can be fabricated to work as well, with the same result…………. There may be an option to use the front hole on a coil spring inner bracket, and fabricate a new hole on both the inner and outer brackets for the rear hole. Guess what, that puts the bumper where it’s supposed to be or close enough. But might that change the pitch? If that works the new holes would have to be nuts for flush bumper mounts. The more I think about this option the more I like it, but OEM correct would be awesome. F. Wish I’d bought a coil spring truck……….HA!.Thanks for the help __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assm. guide "kit" for restoring it from ground up. With assys, the guide accts for 1000s of OEM identifications and part numbers, all written in short order. 700+ images include assm, illust., charts, and points of interest. Much of the info. applies to all 67-72 GM trucks, and to a lessor degree all 67-72 GM vehicles. My build thread, and more on the guide https://67-72chevytrucks.com/vboard/...d.php?t=730025 Last edited by 71CHEVYSHORTBED402; 03-12-2019 at 12:55 AM.