My FJ60 has had spongy brakes since I bought it. It has a new master cylinder, new rotors...pads are good, I have bled the brakes several times thinking that there might be air in the line, but no bubbles come out of the lines. The pedal has a fade in/out spongy feel like it is going with the speed of the vehicle. When I push on the brake pedal, it will go up and down like the rotors are warped. The previous owner had a new master cylinder put on and new wheel cylinders I believe. It looks like either the old master, or booster leaked for a while, cause the paint has bubbled off and rusted under the booster.
It also seems that they have gotten softer since I have put on the weber carb...could this be from a different vacume pressure?

One thing that I found on mine was the hard brake line that runs along the front axel was mashed due to towing. Most tow drivers will throw a couple of hooks around the axel unaware of the brake line and it will get flattened. That helped alot when I replaced it. Second, make sure your back brake shoes are adjusted all the way out. It seems I have to adjust them back out everytime after I wheel. They way you do it (if you already know, sorry) is put the truck in neutral, jack up one wheel and turn the adjustment clicker from the back until the brake shoes drag abit, then do it to the other one. You might also have bad calipers, it is common for a piston or two to stick. Get some low milage second-gen 4-runner calipers from a junk yard, they are bigger and newer and basically bolt on. See David Tays link on www.Ih8mud.com
Good luck,
Ricko.

I took a look at Woody's site, and found a link to braking. This may sound like a dumb question, but does an 84 FJ60 have proprtioning valves? I did not see any on mine during the countless hours under it.

I second the check on the rear drums, they are usually way out of adjustment!

I went head and rebuilt the front calipers and rear cylinders a while back and it made a huge difference in braking feel. Literally, it has the most responsive (proportional) brakes of all my vehicles!