If you want to maintain those speeds you're going to need a lot more work than you think. Driving an Eagle to 120 is scary on a stock (or mildly upgraded) front end, and I've upgraded to poly bushings and a sport rear swaybar. You will need to do a LOT of work to that car to make it stable enough to go that fast, and consider that you're dealing with 120 gallons x 8.6Lbs per gallon, which means you won't be able to stop. Our brakes are terrible for coming to a stop from highway speeds, it doesn't take much to get them fading. I've towed 2000+lbs behind mine for decent distances and it has a huge effect on the braking. Also, in order to pull those RPMs at that speed, you would need 2.35 gears and much larger tires than stock. That combination will also break your in town gas mileage and acceleration, and you will need to make a very respectable amount of power in order to even attain those speeds.
Also, the 4.0 head swap will put your power into the midrange, and add tons of top end. If you never make it past the 3500 rpm mark, you're missing out on a lot of power. A 4.0 head swapped 258 pulls hard all the way to 5000 rpm. Keep in mind the 4.0 was tuned to make its maximum horsepower at 4500 - 5000 rpm depending on year and head casting, and max torque in the low 3s.
Also.. getting caught driving more than 100 mph in most states constitutes an automatic arrest and can include felony reckless driving. I lost my license in the past for points and speeding, it's just not worth it. There's no way a policeman would go easy on someone driving that fast in a 25+ year old large station wagon.
I'm not trying to shoot you down, I'm all for people building their dream eagles, just make sure you have all of your bases covered