[Christ]

No, they don't. 88 and 89 swap, 90 and 91 swap. The rails are different for two sub gens.

You can get seats from a CRX HF in '90 and '91. They're not much lighter, but maybe a pound or so.

IF you want to just recover the seats you have, look at the frames minus the covers and foam, and see if there's any material you can remove.

If you don't need to adjust your driver's seat after you've set it for yourself, remove the sliders and make aluminum tabs to mount the seat to the floor. The sliders weigh a couple pounds themselves. You can also remove the seat-back linkage and hard mount the seat back to the pan frame.

The seat bottom pans are close to solid pieces. You can remove a LOT of material from there without making it weak. The seat does nothing for a frontal impact. The shape of the seat helps prevent intrusion from a side impact, but not as much as the door beams and rockers do. The seat pan doesn't really help with a rear impact, as most of your weight will transfer to the seat back. Adding solid mounts between the seat back and bottom will help to keep them from separating and remove additional weight.

The other option is to find a comfortable "racing" (sport) seat and install it on a fixed mount. They generally weigh less than 10lbs for the seat.