I follow the vintage Mac community, and there are people there remaking classic Mac PCBs as drop-in replacements with the same chips since so many boards get eaten up by leaking PRAM batteries or old capacitors corroding the traces on the board. Most of the chips on the corroded board are still good (or at least the ones that are custom or no longer made) so you can desolder them from the dead donor board in the machine you bought and pop them in the new one