Tubular K frame with a rack and torsion bars

I am interested in the front steer rack n pinion. Can you tell me what wheel back spacing and wheel diameter will fit your lower ball joint steering arms? Can you provide details on the lower ball joint steering arms? Which spindles do these fit? 73-76 only? or the earlier smaller bolt spindles ?

I went to look at your site for updates on the system but couldn't find any details for the front steer option, including pricing.