help making d15 a dually

https://gyazo.com/c1155c2a81e9cb645b94d5c32edd9dae im trying to make the d15 a dually how do i do it?

 

Just make a new config
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Btw, the link is broken. It says we haven't permission

 

In the rear suspension, change the spindles to duallies.

 

ok thanks!
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actually i go to rear spindles and there is only regular spindles

 

I dunno then, take a look at every rear suspension component to see if there is a dually version, or even a frame.

 

Just select the Heavy Duty 8-Lug Rear hubs
There are only two sets of wheels, so the current ones couldn't be used. However that's the only way.
Select the Heavy Duty 8-Lug hub in the front to have matching wheels.