Steering coupler question

Your question is valid, there isnt much flex, but its there, and because its there you have to provide a way to work with it. We used a sliding coupling on my friends ratrod project a few years back. It was 1963 dodge town panel with a 79 dodge 1/2 ton pickup chassis under it. Bought a sliding coupling with ujoint designed for GMsteering box which the 79 used. And mated it with a late model chrysler tilt column. Full frame chassis, seperate body.