Coupler For Borgeson Steering Box

I've installed a Borgeson steering box. I have 2 Mopar couplers. One is from a '70 Duster, the other is from a '71 Duster. They both have different sized holes on the spline ends that connect to the box. I understand that one was for manual steering and one was for power steering. But, neither of then work with the Borgeson box. The small one won't fit the splined shaft on the box and the larger one spins freely with just barely any contact. Are there no Mopar couplers that work with the Borgeson units?
I'm looking at the Bergman Autocraft coupler, but am concerned that it also may not fit.
Anybody running tbe Borgeson box? What coupler are you using?
Thank you.