I installed the 70 series suspension seat brackets in my '86 USA FJ60 20 years ago. They were used. They fit this car exactly. No tinkering at all. Just bolt in. Not sure if the HJ61 has the same seat mounting geometry.
Since I was taking long trips driving off road in Mexico, better seats were a high priority on my list of upgrades. First priority. The stock seats SUCKED> and were killing my back.
My initial plan was just to use those suspension seat brackets with the stock original seats. That didn't work out too well. The stock seats were too high. So I purchased a nice used pair of the correct seats that were designed for those suspension seat brackets. The driver's side has power lumbar and you can contract in the sides of the back of the seat if you want. Marv Specter (whom I purchased them from) called them "King Fahd" seats.
I have to say, that the 70 series suspension seat bracket and seat upgrade was one of the best offroad upgrades I've done to the car. I can now drive ALL day long on bad (we're talking real bad) dirt roads and my back feels great at the end of the day. That was impossible with the old seats.
They don't do much on pavement.. but drive the car on some bumpy dirt roads... and you'll be all smiles.
The seats are a little higher than the original ones were.