The first thing to think about with a processor of that generation is the mobo. It is probably an AT mobo rather than ATX and this will limit what you can put in it. (The mobo will set limits anyway).
You can check this out because the AT mobos had a physical on/off switch where as the ATX had the switch via a Mobo relay.
If you have an AT Mobo then you cannot change this without the case and PSU as well.