Can it be done? I am not sure, but lets ponder this.
B14s have been offered with the GA16de and the SR20DE, the B15's also at one point had the SR20DE in them. If the QR and the SR fit in the B15 and the SR fits in the B14, Maybe the QR will fit in the B14. ??? did you get that?? i dont know even if i did.
The reason the SR20 fits in both the b14 and 15 is because nissan designed a tranny for each of the cars.
In other words, you can swap a b15 SR20 block by fitting it onto a b14 SR20 Tranny. Since no b14 tranny will accept the QR25 block, there is no cost effective way to do this. It's not whether the block fits, it's whether the tranny fits.
Anything is possible it just comes to the point where it is not worth it. The SR20DET makes more power, fits easily, and weighs less then the QR25. The extra weight over the front axle will not help handling