The rad for the V6 is more substantial (core, tank size, etc), then the 4 cyl version. If a tank is leaking , you might consider getting it repaired and cleaned. Those brass/copper rads are quite expensive. The quotes for the part I received in BC were over 1k? They are much less in the states but still $$.
If you have a 3VZE (V6), then you might consider staying with that version. In fact, when we replaced our rad on our 1990 V6 runner, Toyota had significantly improved the core to increase efficiency. Best of luck with it.
regards