I used to autocross against a well prepared 280ZX in FP. It was never as quick as a well prepared 240Z. National champion Andy Craig commented once that it was the wrong "horse" to choose.

 

I autocrossed my 280zx 2+2 with stock suspension. It was a fun event to participate in once... end of story.
The rear end sags when I just take off, and yes I would like to have it much more stiff. It might not be too bad of a car if you lighten it up as much as possible. Get a 2-seater hardtop.

The wheelsbase is just a little wider than a 240Z although the front sway bars are interchangable between the two.

If you want to compete and not just do this for fun, maybe a 240Z or prepared 280Z would be a better choice. For some reason I thought the S30 rear suspension was simular.

 

I autocrossed my '83 turbo and it did just fine. I put Tokiko non-adjustable struts and springs on it. I've also seen other ZXs do quite well. All of them had suspension work, but what autocross car doesn't?
-Kel

 

I autoXed my 1980 daily driver last year at 5 events just to get experience. The best I did was a 7th place out of 16 cars. Mostly Miatas(YUCK!). My car would have been more competitive if I'd gone through the car and replaced some of the original worn out suspension components....238k miles on them...doh! It can be a competitive car still.
First find a 1981-83 NA base model with out t-tops. These are the lightest of the ZXs. They have no AC, manual rack steering, no power windows...etc. Plus the 81-83 have the better head and higher compression.
You should go through the suspension...what you do here will determine what class it'll put you in. I like the Tokico Illumina struts. These should help out a lot on the cars tendency to squat. Stiffer springs are also a nice upgrade here especially since stock zx springs are probably sagging by now. Serious ZX racers drill out the rear control arm mounting holes and weld on slotted washers to adjust the rear toe. Due to the trailing arm design on these they gain a lot of toe out when the suspension is compressed. Off set bushing front and rear also help on the rear toe and camber and for front camber. A good alignment is key in autoxing. You usually want 1/8" toe out in the front and as much camber as you can get away with. The toe out helps the car change directions easily.
There's lots more that can be done to these, but I'd have a lengthy book written before I'm done. Get a plan going and budget accordingly. Good luck.

 

mines 81 and has ALL the gadgets lol cept the talking lady

 

There's no specific book on modifying 280ZXs that I've ever run across. All the knowledge that I've got pertaining to them is from chatting with the guys who used to autocross and road race them over the years. Wish I could still find all their names and email addresses...doh.
Gary