I was in the same situation about a month ago. Like you, I planned on machining a brass gib and running with it.
After getting the machine apart, I noticed just how off the stock Z gib taper was and decided to simply regrind the stock gib to match the dovetail.
I am doing some other modifications to the column and haven't had the machine up and actually running yet, but sliding the z carriage back and forth on the column by hand, the results look promising.
If you have access to a surface grinder, this is the route I would go. I set the vise off on gauge pins to dial in the taper. The taper should be .5* . In the end, I had to shim mine.