Good afternoon!
I know that Optiplex GX1 has proprietary motherboard form.
Found a case without motherboard for cheap. It is slim version, horizontal, with only one cd bay.
Can it be modified to put an standard motherboard there and use card slots? I know it used also an daughterboard originally.
Was thinking about PCI risers.
Not sure if AGP risers exist.
Since you worded it in that particular way, I gotta ask - is this for nostalgia reasons, or just because of the price? Because if it's the latter you'll also need to factor in the time spent metalworking to make it all fit (and then some more to make it look decent), and unless your time is worth nothing to you you'll probably find another slightly more expensive case will end up cheaper.
If you do have a reason to for that particular case, then yes, volume permitting everything can be made to fit into everything else, it's just a question of ambition. This one doesn't look like a good beginner project to me tho.