I have a question about this. So I've seen people mention swapping out the speedometer to keep your original mileage, but I was wondering if instead of swapping the whole cluster and keeping your original speedometer could you do it the other way around and keep the original cluster and just swap the tach? Like instead of adding a whole new tachometer could you just pop out one of the unused circles on the panel and stick an ex tachometer in there or something? Essentially I'm trying to avoid splicing a bunch of wires and screwing something up haha
Also I'm not sure if it makes a difference but I have a 7th gen, not a 6th gen (04)
I'm not 100% sure on the 7th gen, but the 6th gen clusters are 100% plug and play. I've swapped through probably 6 clusters looking for one I like in my 2000 coupe and they all just work. You can see in my build thread I've gone through a few.
In order to keep you original mileage, if you're going from DX to EX, you can pull the clusters apart, as in take the clear fronts off, take the black shroud off, down to the gauges. You can unscrew the speedo from your DX cluster and also unscrew the speedo from the EX cluster, swap them around and put everything back together, put the EX cluster with YOUR old speedo, back in your car. Done.
The much harder way of doing it is pulling the gauge face off (removing the needle, which is tricky, also hard to put back on perfectly) and ticking the mileage around. Also, a lot of people frown on this for legal reasons, but what the f*** ever. I photo document absolutely everything these days so it doesn't bother me one way or the other.