OEM Tachometer from sport to SE

All right, I would like to snag a tach from a sport edition XJ to put on my 94 standard edition, but the service counters from the local stealerships say that the wiring is totally different between the Sport and SE. Is that really the case? They tell me that the signal from the sensor (in the distributor cap) is run through a microcontroller and then fed out to the tachometer gauge. Now if this is the case I would guess that the mocrocontoller is just a counter circuit that outputs a dc voltage to the gauge. If I wanted to use a stock (Sport) tachometer gauge for my SE, what is the best way to go? I am EE/CE major, so building the circuit isn't too hard, if that is really how it works. Please, anyone with xperience with this, would I be wasting my time?

I think your dealer is full of...well, something other than wisdom. The tach signal is present whether you have a tach or not - all you have to do is plug it in. Many people have made this swap. I put a full-gauge cluster on my base model 95 without incident. The only thing you'll need is new senders for the temp and oil pressure gauges.

Yeah, I did this swap too. Just swap in the whole gauge cluster. Its really easy and it works flawlessly.