depends on the reflector but in general yes it should be just fine. assuming you mean just the reflector itself and not the sockets/holder
the 150 bulb is slightly longer then a 70. check the one you have because they are very close in length and many of the holders have two mounting options one for 150 bulbs and one for 70 watt bulbs.
BTW i converted both of my 70 watt halide nanotuner kits to 150 halides and all i changed was the bulb, ballast and remounted the sockets for. used the same reflector.