Yeah, I think it's a cost thing, people wanted manual transmissions to save money so they skipped the tach option, auto trans cars usually have more options so they just throw it in...
That said, it's a fairly simple task to add in a tach, I just did it to my '97 a week and a half ago... I found a tech article on another Ranger board, I'll give the cliff notes version:
-Find a '95-01ish cluster with Tach (easiest to find on Explorers), they all seem to be 6k rpm so whatever... I got one from an '00 Explorer Limited... There's a simple latch on the PRND21 indicator on the cluster, I just cut the cable because it was 95F outside but would have been faster to hit the clip... your blockoff plate will go in easy.
-Pull off the lens, then pull the outer gauges out, just pull on the faces, they are a press fit, you aren't going to break them, then pull out the tach. Do the same with your cluster, get them set close together for the next step...
-Get yourself 4 wire jumpers with aligator clips on both ends, if you have to make your own make up two Y's instead of using 4 separate ones... also gather up a new AA battery.
-There's 4 solder tabs if you look at the back of the stepper motor for the speedo, connect a pair of clips to the top ones and a pair to the bottom ones, the top goes to positive on the battery, bottom to negative then note where on the speedo that goes, it'll likely be 70 to 71mph.
-Now take a fork (literally from the kitchen...) and pry the speedo needle off, now you can take out the 4 screws with a 5mm head that hold the speedo/odo to the face and you can put yours in the new face.
-Now hook up the wires again to the battery and while powered up push the speedo needle on half way, cycle the power a few times to check, once you are happy push it home.
-Now reassemble the cluster, take note of any different lights that this cluster might have, remove what you don't have for good measure, and now would be a GREAT time to change the backlight bulbs... my '97 didn't have a "check fuel cap" light on it's cluster and that came on for whatever reason, and didn't have a "check gauges" light and it comes on but not constantly...
It doesn't matter if it's a 4, 6 or 8 cylinder donor, I think my donor was a 5.0L and I put it on a 2.3L... there's a different pin in one of the connectors on the back, but being the original engine your wire is in the right place...
I didn't add a tach to mine because I needed it (it is nice to have since it's gutless in certain speed ranges), more of a curiosity thing so I can keep an eye on my engine speeds... might be able to tune my driving some for MPG... Plus it'll be WAY easier to teach my wife to drive a manual with some indication of engine speed... it's too dang quiet to just say "go till you can hear it"
Just in case it comes up in a search, the second gen dash is even easier to swap, you literally just take the speedo part from one cluster and put it in the other, you don't have to take the needle off... but you need to identify the right year range, IE '89-mid '92 then mid '92 to '94, and I think the 4.0L tach's are lower rpm...
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. Like my '90, in the dead spot next to the middle dash vents where the 4x4 buttons would be is where I put my boost gauge, I veer from there with the manual oil pressure gauge that is in a single gauge pod on the pillar, but it's down at the bottom where it's not in the way... I don't like junk in my line of sight... the wife and her visor flipping drives me bonkers sometimes...
