Yes, I also had scanning issues SX-70.
Best way is a camera. Remove the glass from one of those useless UV filters, lay it down in the middle of a piece of black paper that is at least 3 times the long print dimension. Glue the filter to the paper, then when it dries cut out a hole for the lens. Attach to lens. Bend the sides of the black paper towards the subject so you get something that looks like old-fashioned barn doors on a spot. The idea is to prevent reflections of the lens and camera and ceiling etc on the surface of the print, even out of focus. The bending is to keep light off the black shield itself from being reflected by the shiny surface. Use a longish lens to minimize keystoning.
One of the most lovable distinguishing features of an SX-70 print is the little framing package itself. Light the print to make it a picture of the whole package rather than just the image, nice drop shadows around the edge etc. If you do decide to zoom in to the image only, might be a good idea to cut a black mask just a little bigger than the actual image and lay it around the image when shooting. Will prevent the bright white surrounding area from creating flare in the lens which might reduce image contrast.
Edit...and of course dust is your enemy. You will in particular get fibrous threads attached to the edges of the white mask. You can try to poof them off, butbest way to zap those little devils is by very delicately dabbing them away with a piece of low-tack masking tape, like the blue stuff down at Lowes.
