76 could be Mk3 or 4? there was never any official works Mk4s raced and all the official Mk3 race cars (one series of only a few races) were all standard GTs, you'll need to look at South Africa for race cars on the Mk3 but they were mainly UTEs (Pickup trucks) there awere a few Mk3 and 4 thunder saloons that were raced back in the day though?
There was one semi works Mk5 cortina rally car