Will the stock 300zx seats from the z32 series (1990-96) work in a 76 280z???? If so could I use stock brackets or need to find some different ones?

THe answer to your question is yes...

But they will be a very very tight fit, because the seats are soo wide.. and you need to modify the brackets of both seats to get them to fit.

But most will say.. they are too wide to fit... only because the fit is too tight.