I can almost guarantee your steering box is worn out because someone has replaced the oil fill plug with a grease fitting. That likely means the sector shaft bushings and/or sector shaft are worn to the point they would no longer hold the 90W oil that was originally specified. Filling one of these boxes with chassis grease accelerates the wear because the grease gets voids and allows metal to metal contact. Grease also doesn't flow into the bushings, increasing their wear. Keep in mind, a '49 is a 15/16 sector shaft and there are none available repop, I've had a machine shop build them up and turned down. All the bearings, bushings, and gaskets are available at your favorite Willys supplier. The Ross steering box, while great in the '30s (the era it's from), it was woefully inadequate, even by the 1940's steering gears in common use at the time. By the late 50's, early 60's, the Ross box was only suitable for garden tractors (Power King, Cub Cadet, John Deere), even though Kaiser retained its use in trucks until '64, I am unsure of when the CJ finally got real steering. The Ross box is really the Achilles heel of these trucks. Not good for many miles, my 1950 truck had 34K original miles on it, and the sector shaft flopped up and down 1/8" before turning the wheels. I have rebuilt several of these boxes, not one has had more than 50K without needing repair. A Tightsteer lash adjuster also helps.
You also need to check the king pin bearings for play and proper preload, they can greatly affect steering response, road feel, death wobble, and tire wear. Also make sure the arm on the driver front knuckle doesn't move on the knuckle while someone turns the wheel. This is a common spot for these to have play due to loose studs and worn threads in the knuckle casting.
This being said, would I try to push one of these to 65+mph, even with all the stock components in perfect shape? Probably not. While adequate for the speeds they were intended (45-50mph), the steering system on these is basically hay wagon steering. Same for the brakes, okay for what the intended weight and speeds, not great if pushed beyond. I know slowing down to 45 sounds slow, but it really doesn't add much time at all to a trip, and enjoying the ride is what these old vehicles is about. I frequently have annoyed people blow by me on my 10 mile 2 lane highway trip to the "Big Town", just to pull up right behind them at the first stop light in town (I have been know to facetiously toot and wave).