Not speaking from experience but I wouldn't do it. I think the standard practice is just replace with a smaller loop and do without the larger cooling loop for the PS fluid.
The thing that has attracted me to the Tribute models is the modern car underneath the beautiful lines so you still have PS, ABS, AC, airbags, pretensioners, body designed to meet minimum crash regs, heating and demisting that works, heated seats etc. The steering geometry in the Z3 would have been designed from the off to use PS and to either just empty the fluid or put in a non PS rack would be a no no.
A few years ago a drive belt broke in one of my Saabs as I was driving taking out the alternator and the PS pump. Jesus wept the steering was so heavy even at speed without PS.