Im going to change my tire size to 285/75r16. I currently have the stock 16" tires. Is they any products or fixes to correct so the abs and trans will still shift like stock?

Most use a scanguage or GPS for speedometer - the scanguage can compensate for larger tires.

Some guys have had luck with the dakota digital products. I would suggest through research if you go this route - the number of transmissions and wire colors can be very confusing.

Nevermind, I read the wrong tire number. You might have a 10% increase over what the speedometer reads.

Another device that works is the Dashcommand app for most phones/tablets. I have it displayed on my radio as well. You can easily enter any speed correction you want. I currently don't use it since my tires are currently only 265/76R16 but just wanted to make you aware of another option.

When I went from 265-70-16 to 275-75-16, according to GPS my speed matches the speedo exactly. So you wont be so far off it would be an issue, IMO.

I'm currently looking for tires on a 5th gen, but I think the same would be applicable here.

Obviously, the methods above correct the speedometer., but what about the odometer in the dash? Is this something I can get the dealer to re calibrate?

Why bother recalibrating the odometer? The larger tires will slow it down. (Good thing) but as others have said, compare your after tire speedometer reading to a GPS and see where it stands. Most likely will be much closer than you think. If the speedo is right (or close) than the odometer is too.

Sure, good in terms of overall odometer reading... However, now it's a false reading and technically illegal, especially if I know about it. Legalities aside, I don't find this morally acceptable (for me) and I don't want the extra headache of having to remember to multiply every data point gathered by x%. Lastly, while my work fuel is payed for, if I drive over x miles for the month I get extra dollars on the mile past x, so not doing this would be throwing away money.

How far off do you really expect it to be? They're not 100% correct when new.

Going from a 265/70R17 to equates to a speed difference of:

255/80R17 - 4.41%
285/75R17 - 6.58%

I doubt every truck new is 100% too, but I bet it's within an acceptable margin of error. If I drive this vehicle to 200,000 (like my last taco), without correcting the speedo, I'm actually driving an extra 7480 miles @ 4%... That's too much for me.

Consider my example regarding work above. x = 2000 miles; which I frequently pass. Not accounting for the extra miles (I already reach) lets say I only meet the 2000 mile mark every month for the next 200,000 miles, thus don't quality for the extra $ (or .25 cents/mile).

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(@ 4% speedo difference)
2000 * 1.04 = 2080
2080 - 2000 = 80
80 * .25 = $20

200,000 - 13500 (current mileage) = 186,500
186,500 / 2000 = 93.25

$20 * 93.25 = $1865
-------------------------------------
(@ 7% speedo difference)
2000 * 1.07 = 2140
2140 - 2000 = 140
140 * .25 = $35

200,000 - 13500 (current milage) = 186,500
186,500 / 2000 = 93.25

$35 * 93.25 = $3263.75
-------------------------------------

Sorry, but if correcting this cost me even $500.00, I'm not planning on throwing $1300.00 - $2900.00 I could use on mods out the window for being lazy.

At 200K miles, nobody really gives a sh*t is its actually 200K or 207K. If you left it bone stock and went 200K indicated in the dash, in reality you could be 195K, you could be 205K.

So I should just ignore the fact I'm throwing away $2,000...WTF lol.

No. But you're over thinking it. You're probably throwing away the same amount stock. Or getting over on your employer now.

Do you think Toyota put different speedos in the autos than they did manuals? How about the 4.10 geared trucks vs. the 4.30 geared ones? It's all the same. Take it for what it is.