What Base Rails Fit 2021 GMC Sierra 1500 With 5'9" Short Bed
Updated 01/05/2026 | Published 09/09/2024
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Question:
I have a 2021 Sierra 1500 with the 5’9” bed and I would like to install a standard fifth wheel hitch to use with the Reese Sidewinder. I am towing a Winnebago Micro Minnie 2405 which is only 7’ wide rather than 8’ so I think this should be possible with the 22” offset that the SW provides. Will the kit for the 6’6” bed work on the shorter wheelbase truck? Also, I have a Curt Q20 hitch, would that be sufficient and will the SW work with it?
asked by: Mark
Expert Reply:
Hey Mark,
Yes, the 5th wheel base rails for the 6'6" 2021 GMC Sierra 1500 will also fit the 5'9" short bed, with the correct rail kit being the following:
- Reese Quick-Install Custom Outboard Installation Kit w/ Base Rails # RP56015-53
Keep in mind rail kits won't fit your Sierra if it has the CarbonPro bed or Adaptive Ride Control. This'll allow you to mount a 5th wheel hitch with the Reese Sidewinder # RP34FR, but you can't use the Q20 because it isn't compatible.
It has a spherical head which isn't stable enough to use with the Sidewinder, so you'll need a new hitch and wedge that is compatible. You should be able to sell the Q20 pretty easily and you can replace it with the B&W Patriot 5th Wheel Trailer Hitch # BWRVK3255 and Wedge # RP74FR.
Finally, the last thing you'll need is a 5th wheel wiring harness, part # 20110.
Product Page this Question was Asked From
Draw-Tite 5th Wheel/Gooseneck Wiring Harness 7-Pole - GM, Ford, Dodge, Nissan, Toyota w/ Factory Tow
- Custom Fit Vehicle Wiring
- 5th Wheel and Gooseneck Wiring
- Vehicle End Connector
- No Tow Package
- 7 Blade
- Plug and Lead
- Plug-In
- Tow Ready
more information >
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Robin H.
1/5/2026
Hey Mark, how did things go with the Reese rail kit and the B&W Patriot hitch on your Sierra? Did the Sidewinder setup give you the turning clearance you needed with your Micro Minnie? Your update could make it easier for others towing with short-bed trucks.