zr 160 backbox on a 200

Yes.

The exhausts on the 160 are a slightly larger bore, and the backboxes may be the same (I'm not sure). But it wouldn't make any difference you would notice even if they were.

To confirm this, I had a Powerflow from a ZR160 on my Rover 200 for a while

i had a zr160 back box on my brm which i brought from BSM only problem i found is it sticks out a bit someone on here named it power trip instead of power flow lol

What I wanted to hear, thanks guys. Shouldn't stick out more if I have a zr bumper instead of a 200 bumper.