The factory head gasket for 1.8 Miatas is pretty tough. So here you go, an OE Mazda head gasket. Suitable for up to 1.5 mm overbores, 0.032" thick. Multi-layer steel (MLS) construction. Mazda part BP26-10-271
The coolant passages are different on the 2001-05 heads, so the gasket is slightly different. If you're mixing and matching heads and blocks, match your head gasket to the head you're using.