Yes, you can use parts from GTO and Lemans as these are just trimmed out Tempests. Don't expect them to fit directly though. For instance, the GTO will have a different carb from your Tempest. But you could exchange the entire engine no problem. In general you are working very near the end of the Pontiac life and they soon became nice Chevys. Already many parts will interchange with Chevelles and Buick Specials and Olds Cutlasses. But many parts are still uniquely Pontiac. The interchangeability of the parts depends on exactly which part you are working with. Sorry.
