Parts can be salvaged from some old ovens. This should only be done by an experienced person that is sure that parts are compatible. Gas ovens should be thoroughly checked for leaks after any salvaged part is added.
To salvage parts from an older oven, first try to find a manual for the oven that shows how it fits together. Old oven parts can also be used for creative art projects. Make sure that ovens repaired using salvaged parts are thoroughly tested for safety before using them regularly or reselling them. Hard to remove parts may be better to buy from a dealer than trying to remove from an older oven.