I installed the Audiovox CCS-100 on my 87 Civic 2 years ago and it is still working great. You will need a vacuum reservoir and a one way vacuum valve.
I copied and pasted this (below) from a PM I sent to another member that was thinking of doing the same thing:
I was concerned that the unit said that it wasn't recommended for Hondas- my best guess as to why is that the CC unit has about a 1.5 inch total "pull" range and my Honda only uses about 1 inch of pull to get from idle to wide open throttle. So, if you install it where the pulling cable is tight when the unit is off, when you turn the unit on and go up a big steep hill, the unit will pull the first 1 inch and your throttle valve would be wide open, but if your car was still not going fast enough, the unit would keep pulling because it had that extra half inch that it could pull. This extra pulling could possibly damage the unit or your throttle shaft/plate/linkage.
The solution is simple, just add an extra half inch or so of slack in the cruise control cable so it never can pull too much on the throttle valve. Maybe the CC company had a bunch of Honda owners not realize this and damage their car or the unit and they got tired of giving refunds for it.
I first put the unit in the engine compartment, but then the pull cable always seemed to be in the way when I was tinkering with/adjusting the carburetor, so i connected it to pull on the throttle cable just above the gas pedal and I mounted the CC unit up under the glove box. It does make clicking and tapping noises as it adjusts speed but I don't mind.
If you want to mount the unit in the engine bay, you'd just need to have the CC cable pulling from the same point as your throttle cable pulls from or you might need to make a little bracket and make it pull from the valve cover. There are lots of little throttle adapting cables and brackets in the the kit so if you have some mechanical creativity you'd be able to figure something out that would work- just remember to measure it all out and add that extra slack in so it can't pull too hard.
You should be able to find a vacuum reservior on 1970-1985 chevy trucks and cars. It looks like a smooth round black softball mounted on a fender or on the firewall. You will also need a 1 way vacuum valve- its about the size of 3 or 4 lifesavers still wrapped together and it will have 2-3 vacuum hoses coming off of it- just be sure you can blow in one end but it doesn't let you blow through the other way (so that it is one way only).
It will make it easier since you have a 5 speed trans. You can use either the VSS or the tach signal from the ignition coil to tell the CC unit what speed or rpm you are going, but you don't need both. My coil has 4 wires (2 connecters) going to it. 3 small wires and 1 thicker one. The tach signal wire is the small wire that is paired with the thick wire- that's the one I tapped in to.
I put the same model of CC unit on a guy's truck about 2 years ago and he is very happy with it.
There are lots of little sensitivity settings/adjustments that you can do on it to get it working like you want.