white leds need 3-3,5v, ir led needs 1,5-1,7v, however linear drivers that used in 90% flashlights are constant current, voltage changes depending how much the led will pull at rated current.
similar story with red leds, they only need 2-2,2v but they work just fine with drivers used for white leds, for the reason i mentioned.
so there is a possibility ir led will also work ok with constant current driver, but i didn't try it myself, what i would do is to mesure V while ir led runs, if it is too high, i'd add resistor.
few times i did ir lights i just used 1 alkaline\lithium cell, with no driver\resistors, voltage wise, those cell are exactly what the led needs, and in my cases current was within specs,
as for heat sink, there is no difference between heat dissipation of white leds or ir\uv\...any color, so if your heat sink was sufficient for white led it will be as good for any color led, of the same power.