to build a spindle it just takes $$$....and the sales to support the investment. I have several spindles I would build but last I checked, an order / purchased of 1K is laughed at.
However, as long as it is a front steer spindle, I'm not so sure that it wouldn't as simple as to build the control arms with the required ball joint receiver(s)
What is the application (yr / make/ model) of the spindle you prefer?...I'll check it out