* The main question is with the 1300 milage towing and going through TN I24 do you think this would be a good idea to try. I only need to tow it once like this. Will the grades in KS, MO TN be a killer to the 4 Runner.
Well, I have made that same tow many times, except I take I-10 to/from Jax and then down to St. Augustine instead of I-75 all the way down to the center of the state. There are two significant climbs/decents on I-70 in Mo. Neither is longer than a mile or so and shouldn't present any trouble as long as you take your time. If you take I-64 east from St. Louis then I-55 south to I-24, Illinois is very flat until you reach the one mountain range between I-55 and the Ohio River. There is one climb/decent there and its only slightly longer than the two in Mo. Buy gas in Mo and run all the way to Kentucky where prices are lower than Illinois.
The biggest mountain (climb/decent) on the whole route is in Tennessee. North west of Nashville there are a couple of minor ones (similar to Mo but have turns in them) but the biggie is Mont Eagle mountain. Its a six mile climb to the top and then a couple of miles across the top before an equally long decent. Either side isn't very steep but the grade seems to go on forever. My van climbs it comfortably in 3rd at 70 mph. Both sides have multiple "runnaway truck ramps" so keep an eye on your speed and brake temps.
From there you have the mountains around Chattanooga which aren't any worse than what you have already seen. Then from Chattanooga all the way to Macon, Georgia, there is hardly a level spot. Nothing big but it seems like you are always going up or down. From Macon south, its as flat as the midwest. Be on the lookout in middle/south georgia for local cops/sheriffs running radar looking for out of staters as easy marks. Keep it under 80 and you are typically fine. Also keep an eye on your speed in the construction zones in south Georgia. The locals like to pick off out of staters there. Typical construction zone speed limits are 55 or 60.
If your truck is an automatic, make sure you have an external transmission cooler before you start the trip. And it would be a good idea to change the transmission fluid if it hasn't been done in a while. When towing, you can tow in OD if it will stay in OD and not hunt between gears and the torque converter clutch stays locked. If it doens't, tow in 3rd.