Here's another thread that references the n/a swap: http://forums.hybridz.org/showthread.php?t=116623
Another reference of doing an n/a swap: http://forums.hybridz.org/showthread.php?p=686973#post686973
It can be done, but it involves tons of rewiring. You will have to cut all the 280zx ecu wires, trace them to where they should go on the Z31 ecu & re-connect them all... It's not a horrible job, just very time consuming compared to other do it yourself stand alone instalations. It's very easy to do on the 280zxt because the ecu connections are the same as the Z31 & the ecu's are programmed similarly.