I don't know if they would be the same. But the i3 heat sink "may" not be as good as the i5 heatsink because the i5 is a better/faster processor.
However it should work.
They're different coolers. The i3 heatskink is all aluminium whilst the i5 heatskink has a copper base. The i3 TDP is 55 W vs the i5 77 W which is probably what accounts for it.
So you can use an i3 cooler on an i5, in that it'll physically fit and conduct heat away, but you probably want to keep an eye on your temperatures. If they get too high then you'll have to get something else. But you should be okay in that you won't burn out your i5 in three seconds trying this.