How many miles on the car?
This is common around 100K or so miles.
You can go with the plastic tank style radiator and it will last another 100K, or something like the Zionsville Aluminum radiator that will last longer, but it a bit more expensive.
If you haven't done it, probably a good time to replace the thermostat housing and the water pump.
'95 Alpine M3 LTW
'00 Dakar M Roadster
'02 Topaz M3
Red/White SRF #4 (Chassis 561)