8.5 inch 4.11 posi?

Hello,

I am currently building up my 77 Nova Rally to be a street car. I am converting from the stock 305 and 3-speed auto trans, to a 355 Stroker and 4-speed muncie trans. Right now the car has the stock 10 bolt limited-slip rear end in it. I was a little concerned that the stock rear wouldnt be able to handle the new load if I got on it. I have been looking for a rear end and I came across a guy who said he has a 8.5 inch 4.11 posi rear end with disc brakes on it, that came out of a working car (Mercury Cougar I believe) that I could have if I came and picked it up (1.5 hrs away) What I need to know is, is this a good rear end? I know very little about rear ends in the first place and absolutely nothing about Ford rear ends. Any input would be appreciated. Thanks!
DJP2