The vehicle has the stock rotors but someone put on the '79 pickup calipers. Recently I noticed the braking problem in heavy rain, so I think some shields should go back on if they aren't on, which is not easy, or some different brake pads would help, which is easy. I have some 4-pot calipers, but that would not be easy to install, and probably not even needed.
I haven't looked at the front brakes for several years, so I don't know what condition they are in, but the pads are definitely not worn out.
The rear brakes are the stock drum brakes.
And yes, I'm considering a lot of different things you could do. The stock calipers are not too expensive to buy and would be easiest to put on to get back to a know point of operation, and go from there. I don't see a real reason to keep the pickup calipers, because they don't seem any better, and aren't the same units as the stock calipers, and probably use different pads too, so you just can't go to a brake shop to ask for pads because they'll turn you down for not have a factory/stock vehicle (if you modify your vehicle, you are totally on y our own except for oil changes.)
I haven't used the 4Runner calipers because they need to be rebuilt and you also need the larger master cylinder, which is more-or-less NLA, so the whole 4-pot thing isn't even necessary at all, because the stock calipers should be adequate anyway.
So now I am back to the idea of putting on some kind of dust/water shield and/or different pads with stock calipers..