another dif ?

In my 72 240z I have a 3.9 r180 dif. I also have a 4.11 diff in my garage. My car is fun now but one day I would like to go with a turbo. I have read an r 180 is fine if the turbo is stock . Is this true ? and how much HP can i go to with the 180 ?

and would 4:11 be too low of gearing for a turbo set up ?

thanks

DC