Radiator and seats/ starting problem..
 

My radiator in my 80 RX has a leak. I fill it up and the car runs fine. But when it starts to run low the car won't start.. Just wondering why that is? And is a radiator and seats out of a 84 gslse compatable with my 80?

You have a "short" radiator with the oil cooler mounted underneath, the 84 rad is longer and would require a modded oil cooler mount. The benefit is the longer radiator cools better, which is why I put one in my car. That would not probably be important to someone in Nebraska so I would just go with the original radiator.

The seats will swap no problem.

Its coincidence, that won't solve your starting issue, you have a 1980 RX7 (the bastard child year) its just what these things do. Seats will fit, you may have to cut away the carpet around the mounting holes as they got better fitment or used less metal later on.

I thought the GSL-SE got the oil cooler mounted on the bottom. I can understand a 1984 with a 12a and beehive having a longer radiator.

the se oil cooler is mounted forward of the rad by it's own mount to the frame.