Steering box question

1964 Valiant
I got manual and power steering boxes. I want to put that power steering box on my car. The problem is, thats with large spline shaft. And the bigger problem is, that early a-body pitman arms(large size spline) are very pricey...
Is it possible swap that manual input shaft(which is small) to that power box?

Thanks for your help!

-Janne from Finland (..and sorry my bad english)