I recently bought a used 92' 4runner with the 6 cylinder engine. It was sold for an insanely cheap price, but I knew from the start I would have to do a few repairs to get it back up to acceptable operating condition. I know a few things that are wrong with it, but I will likely need to diagnose and fix many more problems, the diagnosing of the other problems is what I will need help with. Right now I know 3 things that need to be fixed. The first is to replace the heater core; once the car heats up to operating temperature, a larger amount of coolant vapor pours out of the defog vents into the cabin. The next is replacing the main front seal, the one on the crankshaft. It is leaking oil, although not at an extremely alarming rate. The rear door/tailgate is bent in, so I will need to fix that at some point. There is a massive hole in the muffler, It looks like it rusted and got hot and just corroded a massive hole, I think that I will probably want to run new exhaust pipes. I'm also planning on replacing the spark plugs because I don't know how old anything is. The battery is also bad so I will have to buy a new one.
Those are all the issues I currently know of. I noticed some symptoms to some possible issues.
When accelerating and the rpm's are between 2-4K, the engine kinda putts, like the combustion stops for a second (it kind of sounds like backfire, but not as explosive). The car seems to be lacking a lot of power, I can notice that I cant go up hills very fast right now. Also, when I let off the pedal, or when I'm shifting gears(park, reverse, drive), the car will die. I'm sure this has to do with the battery to an extent since it holds 0 charge. Could you recommend any other cleanings I should do, or relatively cheap parts I should replace? I don't want to funnel a ton of money into this car.

Any help would be greatly appreciated. I assume highly experienced people would know the common problems after a 2nd gen 4runner has been neglected for a while.

 

Do you know when the valves were last adjusted? When you do the crank seal it would be a good time to adjust the valves and replace timing belt. That's also a good time to replace the water pump and thermostat.