Digital Dash Apperance

The preferable (and easiest) method is to swap one from a newer Z. Unless you are familiar with the integrated circuits that enable the vfd.
I actually prefer the 84 display but am using a 86 digital display because the 84 dash had some intermittent issues that i didn't feel like getting into.

I don't mind the 84 display. I just think the 85-86 display looks much cooler. I was hoping it was something a bit more simple.

it is. it's easier than analog to digital swap

Probably so, but it may not be practical since the current dash only reads 19,355 and dialing the odometer back is against federal law.

I actually have an analog dash and the wiring harness too but prefer to keep the digital one.

I'm not an attorney or am I familiar with the federal/various state laws regarding odometers....

While it maybe illegal to change the odometer reading to a lower number and then sell the vehicle stating it has the lower miles (i.e. fraud), is it illegal to match the replacement odometer to the current vehicles odometer?

From https://www.dmv.org/vehicle-history/odometer-fraud.php

"Odometer fraud, also referred to as odometer rollback, is the illegal act of changing or altering the mileage readings on a vehicle to make it appear to have a lower total mileage. In the United States, odometer fraud is a felony offense."

I didn't see anything concerning odometer matching. If you replace the speedo and match the miles, what's the issue?

BUT this may all be moot in the case of our cars since they are over 10 years old. I would check with the DMV in your state.

Luckily the manual odometer module in the digital dash assembly is removable, so you can take your original odometer and transplant it into your replacement digital dash assembly.
I did that when i replaced my failing 84T digital dash assembly.

That's very useful information, but I am still not sure the act of replacing the odometer is legal. According to the DMV website, odometer fraud includes the following:

Disconnection of the odometer.

Resetting the odometer in any way.

Altering the numbers.

Replacing the odometer from a vehicle without providing required notice.

I suppose if I were to disconnect the odometer, remove the old one from the donor dash, then replace it with mine that would not constitute odometer fraud. They also require you to report replacing the odometer and that could lead to suspicion. Moreover, in states like mine (RI), they often have an overly broad reading of the law. For example, texting while driving is illegal in the state of Rhode Island. In one case, an officer cited a man for texting but he was actually using the GPS. Long story short, the judge fined the man a $100 fine, and sentenced him to attend driver training classes even though his defense attorney told the judge his client was using his GPS.

They way the judge and later, a panel of magistrates read the law was no texting, or reading was allowed including using the GPS, or anything that's a distraction to the driver. RI is the only state to have that law. With that said, do you think I'd simply be able to swap out the dash and odometer and get away with it haha?

Of course, it's not like I have to tell anyone that I replaced these components. However, as much as I like the 85 Dash over the 84, I'd like to be careful and make sure everything is OK before going through with something like that.

Disconnection of the odometer.

If you have to remove your cluster to replace a burnt bulb, you wouldn't think twice about it. Removal of the cluster to service a bulb is to disconnect the odometer. You criminal.

Resetting the odometer in any way.

This is illegal, and is not necessary to put the odometer from one dash to another.

Altering the numbers.

This is illegal, and is not necessary to put the odometer from one dash to another.

Replacing the odometer from a vehicle without providing required notice.

You are not replacing the odometer.. The odometer that was originally in the car with the 84 digital dash is the same exact unit as if you were to put an 85 digital dash in.
If it makes your pucker anymore relaxed, you could even gather all the proper tools, a donor 85 dash and do the disassembly,transplant and reassembly
in the front seat, so the odometer never even leaves the vehicle.

Unless you are already under surveillance for that elaborate money laundering scheme involving your grandmothers beanie baby collection and wiener dog race tampering, then the federal/local government is not going darken your doorstep or care in the slightest what you are doing to a 32 year old import car.

Well said.

Not really important to the topic at hand but is the bottom picture actually from an '85? I thought starting in '85 the numbers along the bottom of the tach were evenly spread out and only the '84's had the big gap between 1 and 2 and the crammed together 5-7.

Also unrelated, but red is pretty cool looking. https://www.zdriver.com/forums/300zx…ash-red-40650/