is yours a series 1 or series 2?? Either way it can be done only thing is if you are putting it into a series 1 a couple of other things will need to be done. Series 2 will drop straight in.
What's the difference between understeer and oversteer? Understeer is when the driver is scared. Oversteer is when the passenger is scared.
Get a radiatior cap pressure rated to the same pressure as the header tank (same as S2 pressure rating) Then make up a blank-off for the pipe near the cap where the overflow pipe would go on an S2. It's a small outlet near the radiator cap. If this is a secondhand radiator, open the cap and shine a torch down the hole. You're looking for debris clogging the cores, which would be rust particles. Make sure it's free of them, then install it with good quality coolant.