The MC and booster is all you need, PROVIDED you get the hard lines that go from the master cylinder to the proportioning valve on the 96 as well.
You don't need the 96 proportioning valve itself, but you WILL need the lines going to it. Here's why:
The 96 MC has ISO-type "bubble" flared fittings, and the proportioning valve in your 89 has SAE-type double cone flared fittings. You will want to fashion custom hard lines from the 96 MC to your 89 proportioning valve. The one end will be bubble flared, the other end will be SAE flared.
The easiest way to do this is to buy some long hard lines that are flared ISO on both ends. Cut off one end, replace the flare nuts on the new tube with the ones that come off the 96 MC. Then bend and reflare the end that goes to the 89 proportioning valve with a conventional flaring tool.
I found it easier to adapt 2 lines from the MC to the existing prop. valve than it would be to adapt all the hard lines in the vehicle already to the 96 prop valve.
Good Luck.!!