Alot depends on what your eventual plan for the car is. If you intend to run the way it was intended or not. I have found alot of parts on ebay for the one I have. The kyosho gold upgrade shocks can be found but can be expensive. Rebuilding the shocks you have should suffice in the short term as long as they are complete. The clamp on the originals tends to be weak and can be difficult to replace, however the clamps from the kyosho raider will also do. As far as tyres go this also depends on application.
Here is a link to the manual for the car.
http://www.vintagercweb.com/manuals/kyosho_ultima.pdf