When Toyota put on clearance the Bilstein TRD suspension that was used as an OEM upgrade in the FJ, many 4Runner 5th gen owners pounced on the deal. See the thread below for more details:
The FJ coilovers might be a little softer overall, I don't know. Have you asked Accutune?
If you get it from them, they can valve it for 4R anyway. And they should have various spring options so I am not sure what is so specific to 4R/FJ on an aftermarket setup like that. Maybe the 4R valving is slightly stiffer in the off-the-shelf version?