tried searching for a dedicated seat thread that covers seats and what brackets we need.

 

Ghetto fab man. Almost any seat can be used. Test fit, then weld

 

SA, FB and FC seats should directly swap. RX8 and FD seats require a slight modification I believe.

 

FC seats require either enlarging the holes or swapping the rails but they're a generally bolt in affair, I do not endorse enlarging or slotting the mounting holes as the ones that were done on mine by the PO, under certain braking conditions the seat would shift slightly (1/4" max) but it's still rather unsettling.

As far as drivers seats Corbeau makes a set of brackets that specifically mount to their seats and are available from Soloracer.com for $94. They are as far as I know the only company to makes sliders specifically for first gens.

Outside of that it's kind of up to the owner how they want to go about it. Regardless of what you do, measure 10 times and cut once, mounting seats is NOT something you want to "ghetto fab".