Hi,
I’ve little idea about gyroscope. But I’ve used an accelerometer, which gives analog output, so that it is easy to interface using an adc. There are actually veriety of kinds available, differ by the way in which it can communicate with the MCU. I suggest you to google for both the modules, and select one which can communicate with the 8051.
The thing is that, your 8051 don’t have ADC (but you can connect an external ADC), and also advanced communication modules like SPI, TWI etc. Consider those things also while selecting.