I did it and I like the newer unit, but there's 2 complications....
1) The newer unit takes signal from the rear axle speed sensor via the speedometer - you need a 10.25 rear with the speed sensor, and you also need to find a speedometer to pull the board off of. I'd think that any 93-96 should work but not sure. I think I used a 93 or 94. Gas or diesel should work too for the board. This is the actual card on the back of the speedo unit, it's about 3" square. No need for the actual gauge part. On mine I wrapped it in electrical tape and taped it to the top of the cruise control actuator unit.... not the most elegant but it worked. Better would be to mount it in a sealed box. You will want to be very careful to make sure it's fully insulated - very easy to let the magic smoke out of things with an exposed circuit board.
2) The switch wiring is different. I had mine working for a while by switching the 2 wires coming from the switch unit where they connect to the slip ring contacts in the steering wheel but it was finicky. Now that I look at the wiring diagrams, I have no idea why I did that, nor why it worked.... it also isn't working at the moment....
Big problem is that the newer system uses 2 wires while the old one used 1 and ground.... no way to add an extra slip ring easily, so you're kind of sol. I **think** what I was trying to do is make the new system work using ground as the 2nd wire the same way the older ones do but now that I think about it that's a really bad idea. Think the best bet would be to rig a switch box mounted on the dash. You could replicate the control system pretty easily with several pushbutton switches and a couple resistors (120, 680 & 2.2k). On a more advanced plane, you could do it using a short ranger wireless setup between the steering wheel and an interface box under the dash. I've looked at this for this as well as to add steering wheel radio controls... haven't gotten far though.
Another option would be to use an electric vacuum pump. I have one running the HVAC controls and it's worked well. Mine is off a late 80's volvo and it has an intergral on/off switch so all you have to do is wire it up to the fan so it comes on when the HVAC system is on. Only a few cars used them though... I think PSD trucks used an electric pump too, might be able to get one there. Once you get the brake booster out of the way nothing else really takes that much volume.
