My 87 5sp 4x4 cargo did not come with a factory tach which seems a bit lame for a manual transmission. I really didn't want a big huge thing that sat on top of the dash or bolted to the drivers side pillar. I found a 2 -1/16" one at harbor freight for $20.
I decided to mount it where the digital clock on LE models lives and where a useless rattling garbage collector resides on lower trim models. I know it is not in the ideal line of sight spot, but this is not a race car and I am sure I will only be using it as an occasional reference.
I removed the stock pocket and used the face of it as a template on the side of a unsalvageable center console in the same color as my interior. I cut the piece out with a combination of hack saw and dremel tool. Cleaned it up and rounded the edges with a file. Scribed the 2-1/16" hole with a compass and cut it out with the dremel. Once I had the gauge secured to to the new piece, I drilled a small hole in each corner, mocked it up in the van and drilled through the holes into the metal framework in the dash. 4 small metal screws installed (I think I will hunt for some black ones) and it doesn't look too bad!
The wiring was simple once I found out that toyota provided a test port for a tachometer on the side of the distributor. How cool is that? I read somewhere that all vans have a black wire that comes through the floor under the dash and is there for a tach (whether the van came with one or not), but I did not feel like hunting for it and wasn't sure if it was "plug and play" or not. I chose to run a wire under the carpet to the shift console. From the shift console I ran it through one of the shift linkage grommets, which puts it inches away from the distributor. A quick connect will make it easy to unplug when the passenger cover needs to come out. For the connection to the distributor I just drilled a hole the size of my wire in the top of the factory dust cap and ran the wire directly into the plug. A dab of silicone around the the hole in the cap to keep out dirt and moisture.
The rest of the wiring came off of the factory stereo wiring harness except for the backlight, which I spliced off of the backlight for the cigarette lighter (green wire in the 5th image). From the stereo harness I used the yellow wire for the direct positive, red for the ignition "on" power, and black for ground. The tach came with something like 6 different backlight colors- changeable by a button on the front.
I did learn one important thing once it was all installed and I went for a night time drive: there is a very good reason why your dash lights reside under a visor on all vehicles- the glare on the windshield is quite distracting. I will post again when I figure out how to shield the light without blocking the gauge's visibility!