So long it has PCIe, those cards are going to be backwards compatible with it. Whether you’ll be able to get their full potential performance depends on the rest of the system. That’s a mid to late 2000s server. What are the other specifications of it?

I can tell you you're gonna see some real bad performance per watt out of it.

As long as you can power the GPU you should probably be fine.

I mean what do you want to be doing with it? If there’s a specific task in mind then the only time a GPU can be too new is if it doesn’t support the encoders/decoders you need. Most encoding work should be done by the GPU, but your CPU isn’t doing nothing.

Also you can just cut the end of the slot off (assuming didnt come factory like that) and slot the GPU directly in.