Here's the page on the Toyota Land Cruiser Heritage site where the 1960's TV advertisment claims you can cruise "85mph all day long" on the open road with the F135 powered FJ40.
I have no doubt that's true. I certainly make that easily in my truck, although it's most comfortable in the longer wheel based FJ45.
That said, there's what you can do, and what you should do, and Andrew is correct that it really doesn't feel safe to go that fast in an FJ40.
http://www.toyota.com/vehicles/2007/landcruiser/key_features/history.html
I've had mine up to ~85. It's more comfortable rpm wise about 70 and drives great.
Bone stock 64
