tommy wrote:What seats are those? Might as well look at them too; I don't recognize them, so I'm fearing that they're one-off seats that are not all that safe.
The seats are Sparcos. Worn but functional. Think they, at least, are fine for now.
Thanks, everyone, for all the input! Definitely seems like tearing out the existing cage and (perhaps) installing a new one is the way to go. For the time being I'll just be doing autocross, which of course doesn't require a cage, so I may just install new stock seat belts and mounts, and perhaps a pair of used CRX seats. Anyway, I appreciate all the great advice, and if/when I do install a proper cage, this thread will be very helpful!