Can you change the dash clocks to different ones with a rev clock in them if i don't have one on a corsa 99?

Yes, you can replace the dash clocks in a 1999 Corsa with ones that include a rev counter, provided they are compatible with your vehicle's wiring and electronics. It's important to ensure that the new clocks are from a similar model and that the connections match. You may also need to adjust the ECU settings if applicable. Consulting a professional or a detailed guide is advisable for the installation process.