As an owner of a 78 FJ40 for almost 25 years, I can say there is passion that happens about owning one of these beasts. Up until about 7 years ago, it was my daily driver as it was the only vehicle I owned or cared to drive. It is not an SUV, it is a UV, nothing sport about it. It is not a freeway commuter. At 70 you are red lined and taking up your entire lane. But as an offroad vehicle, I put 3/4 of my first 75,000 miles I owned it in low four and only got the shovel out twice and a tow rope once. If extreme offroading is your bag of tea, then I would do just what Atlas Suspension says to do but I'd add the Weber 38/32 carb for a little more umph.
As for the one you have posted. It is rare to see such a beautiful machine like that anymore. If you look through E-bay and CCOT, you'll find them for $10k or more than that one is priced at for similar condition. With my experience there are three things to look at: the brakes tend to leak, they tend to go through water pumps and starters. I'd say take it for a long test drive, some highway, some city, and if the owner will let you some mild offroading. If you like how it handles, go for it.