the upper ball joint taper dia is larger on the C body so the spindle top tapered hole would be too big as is. Way back a C body UBJ has been grafted onto an A body UCA. Dont remember how they solved the spindle lower mounting bolts/lower ball joint difference on the lower end but it was not difficult. If you solved the upper prob I think mocking up the lower end would make the solution to that part probably pretty easy to figure out