Sadly it's not that simple, LPX was never a standard set in stone. Sometimes you can get away with swapping boards with systems from the same manufacturer, series but even that is not a given. Risers are usually only usable in the board they came from, there is a lot of variety.
Your best bet is trying to iron out the problems with your wonky board I suspect. If that doesn't work out then a like for like replacement.
Good luck and let us know how you get on.
Best,
Chris

+1 for what BSA said.

I'm willing to bet $20 nothing is going to work in a case like that expect a similar model board. i.e. maybe a mobo from a 9626 will work. (for sake of argument)

Risers will always be unique, the screw holes will be different, power connectors will be wired different and or have non-standard connectors. The list goes on. Best advice? Repair the board you have, or get a new one. You mentioned the board is "wonky". Check for bad caps. These were mid 90's machines? 20+ years old now. Doing board re-capping is a extremely common thing to do.

Alright... thanks. I'll just see if I can unload the thing on ebay... doesn't really have any interesting parts in it for me anyways. Thanks all