Will it perform the same

[EnderNoah]

Will the gtx 960m overclocked perform as well as the gtx 970m non-overclocked

 

[JackNaylorPE]

Not sure why such questions occur as every 970 can also be overclocked

But No, not even close

MSI 960 Overclocked = 87.3 fps
https://www.techpowerup.com/reviews/MSI/GTX_960_Gaming/32.html

MSI 970 not overclocked = 116.7 fps
https://www.techpowerup.com/reviews/MSI/GTX_970_Gaming/30.html

The 960 was the dud in the 9xx lineup. If ya asked the question about the 970 and the 980, I'd give you a different answer ... overclocked 970s were faster than the 980.

 

[1N07]

The answer to the question: "Will GPU X overclock to be faster than the next GPU in the same line up" is almost always no.
Usually, only with some very specialized cooling and huge overclocks, is this possible.