Turns out the new Mopar thermostat and gasket are the same thickness. However there is no alignment tab nor are there partitions inside for the proper thermostat positioning. The original one in my car was no where close to this thickness. Yes I understand it will compress over time. I was mainly concerned because I didn’t want the housing to check when I torque (110 in-lbs) down the bolts. (That happened in an escort because the dealer had the wrong part in the wrong box.
Anyway, new Mopar Part # 6821 0218 AA - 001. Thermostat made by Motorad 18-558238/0 with other markings of 91C 195F FDI.
Learned this in my Electrical Class. Any car that’s about 5 years old probably has some rusted/corroded ground/chassis connections. There are a number that are super important in most cars: battery, alternator, starter, computers. Follow those and mark them. Then disconnect the negative cable from your battery and isolate it (use a thick rubber glove or tie back). Then disconnect the grounds and clean them, the car, and the connecting bolt with a wire brush (I use the Dremel attachment). Reassemble and reconnect the negative terminal of your battery. You’ll save yourself countless batteries, alternators, starters, and computers.
Since my last update I drove the car about 30 miles when the left cv boot cracked and leaked moly grease everywhere. A guy who approached me before was in the right place at the right time. I loaded up all of the remaining trim, spare, and original parts in the car. Then I sold it to him. I have no regrets. Sometimes a car just becomes mentally fatiguing. That’s where I was at. Cash in my pocket and an empty garage. Not my problem anymore. I shopped for paint jobs: 1500-4500. I already had about 4000 in parts. A mint condition SRT-4 with 96000 miles is only worth between 6 and 10. I probably lost some money, but it’s gone and I learned a lot from the project and 17 years of ownership. The full YouTube playlist is “Dodge Neon SRT-4 Restoration”. Here’s my 19 second video farewell.