Depends, how much disassembely are you talking about? IE a complete resto versus a paint job? If the car's in decent shape, I would just fix the rust where it needs it, scuff the existing paint and spray over top. You can put in the extra work and strip the whole body down to bare metal, but where do you stop? Do you pull the engine and front fenders and do all in there? Trunk? Inside doors? Remove the K-frame and paint and rebuild the whole front suspension? It's a slippery slope and you have got to know when to call it quits. This can make the difference between a one summer job and a one decade job.