Hey Seth, it's primarily the lower intake manifold gaskets, as well as the oil pickup tube style. If you have a 96 block but 90 heads, I'd go for a 90 kit, but you might need the 95+ oil pick up tube gasket (15053-F6501) if you're using the new style strainer (which does NOT have a groove for an O-ring).

Hi Lim, the 300ZX only uses rubber seals on the intake valve covers. The exhaust valve covers use liquid gasket (RTV)