Any one running a rear wing, how did you size it? or did you have it made or buy a kit??

Looking for Dodge dart experiences as i think the size and shape of the decklid matters. I am thinking that a large flat decklid does not need as large of a wing?

I am sure you know this but the size/length of the wing is not the whole equation. The sill plates and wicker are the big thing to form the "box" on back to trap air and provide downforce. My stratus we played with it some. Smallest wicker made it the fastest for sure, not the most stable. But car only went 190's for speed. I think the wicker is where you want to "experiment". Having an adjustable one is the best way to get there. The height of the sill plates is also important. But don't think any of it matter much below 200

What year Dart?

In my parlance a wing requires air moving above and below. A spoiler mainly requires air moving only above.

I'll address wings here.

In the aero world, everything is drag vs downforce.

End plates improve wing efficiency greatly with very little added drag. Wickers improve downforce and depending on size begin to add drag,but are a quick tuning device to gain DF.

Everything Aero is a compromise, example, usually more rear down force, lighter the front end. all else being equal.

With wings, IMO, best to start out big, and add or remove attack angle as needed and a use wicker to gain extra DF if additional drag is acceptable.

I have a standard SCCA TA CF 65" wing on my Swinger. And be prepared for spending some bucks for the high end stuff

I went with the Bickle carbon that was a one size fits all. Had to trim and fit. It turned out great and lots lighter then the aluminum spoiler I had before. It does not have an adjustable wickerbill but I have never needed to adjust it.

Big difference between wing and spoiler.

I've put spoilers on short wheelbase cars going upwards of 150+ and made them less scary at speed. Doesn't have to be real aggressive with angle of attack or wicker to make a difference. 12 or 13" should be plenty for anything below 200+.

Spill plates matter.

Simple explanation - Capt Obvious to some, likely not to others - but ground zero for understanding rear aero:
The air "feeding" a rear wing or spoiler matters: recessed rear windows like 2nd-gen Chargers most infamously, but a concave deal like the Dart isn't far behind, so to speak.
The side plates have something of a diffuser function, it seems, as well as contributing a bit of directional stability.
If one compares 2 identical shaped cars, EXCEPT one has a larger (flat) trunk lid, the larger should be more stable.
A spoiler flap - like a 2nd-gen Firebird/Camaro, to use an obvious example, causes the center of pressure of the air flowing over the car into the trunk lid & back window area.
Extending the trunk lid via a flattish plane (as in PS cars) doesn't provide downforce as much as smooths airflow.
But angle it up slightly at its rear edge, and it works as a spoiler with less aero drag.

Application of either depends on speed, aero "profile", and what one's acceptable trade-off might be.
FWIW, The Daytona/Superbird inverted Clark Y airfoil had different goals/benefits than a drag car.

An intriguing factor to me is if/how time at speed vs rapidly increasing speed over say, 8 seconds, might have an effect on lift/stability at the rear of a car.

I would add on a wing, the end plates mostly prevent the high-pressure flowing air above the wing from rolling over the ends of the wing to reach and fill the lower pressure air that is largely creating the DF so desired, that is what greatly increases wing efficiency in drag vs DF.
The end plates add hardly any frontal area to cause drag.
In additional the end plates reduce the drag inducing vortices generated off of each end of the wing, and as already mentioned increases directional stability by helping to move the center of aero pressure farther rearward of the COG, much like the fins on any rocket does.

The calming effect by extending the rear deck area thinly regardless of any DF gained, also helps to reduce drag by allowing upper air flow to better re-attach to a larger lower air flow supply, vs a typical Kamm tail.

FWIW here is the wing off a an old PS car. Ihra version so 215ish MPH back then. There are a TON of aero tricks on these bodies for sure. Like the leading edges of doors, the leading and trailing edges of the front wheel openings and rear wheel openings. The trucklid, just the shape of the body overall and how the air is directed under the car. Alot for sure. but this will give you an idea of the "box" formed on the back of the car and how low the wicker and sire plates are in relation to the decklid. You can click the image then click again to get a larger picture...

thank you for all the replys. Yes it is for my own car 1973 dart. Yes i should have said "spoiler" as most refer to a spoiler incorrectly as a " wing" I know a wing is raised and has a top and bottom surface.

My car has run over 150 in the 1/8 and on bumpy tracks it is losing the tire in the last 100 or so feet. Data log shows the rpm and d/s spiking up and down. Im sure i can loosen the rebound on the rear shock to help this, but i only have double adjustables and not sure how much that will effect the way the car is acting in the 60'.

Other than that the car drives great, except when it wants to lose the tire and it feels like tire shake in the car. Honestly i dont want to put a spoiler on the trunk because it just ruins the look of the car (dumb reason i know)

thanks again for all the information

It doesn't sound like you need much aero help here.
How about experimenting with maybe 6? simple stick-on vortex generators rear roofline mounted to help get some more air onto the rear deck area to see if you get some improvement?
Good thing is you are fast enough aero is definitely at play.

Sounds like a classic lift scenario - I'd be thinking a spoiler about 3-4" tall, angled 30-45 degrees, across rear of trunk lid.
Best to grab a used lid to experiment with.

(When Missile VII was stuck in the 150s, a spoiler like that picked it up to 170 - it was spinning its tires due to lift at the big end.)