Get a good alkaline based radiator flush. Drain your cooling system entirely, including the block. Then use the flush as directed. Then, drain the system again, remove the block drain bung, the thermostat housing and thermostat, all radiator hoses and heater hoses, baically anything that allows you access into the cooling system with a hose, and flush with water until absolutely clean. Check the block drain bung, there could be a lot of crap trapped behind there. If so, knock it out, and flush again. Then reverse flush everything.
If you have the equipment to do the job, remove the top tank from the radiator, and ream the tubes with something like a dipstick, but make sure its long enough to go all the way through to the bottom tank. A radiator place will do this job, but if the fins are corroded then its not worth it, may as well get a recore. There is a Toyota HiLux (Early to mid 80's, I think) core that will do the job.

Then use good quality coolant in the system.

And be wary of buying a second hand radiator, especially if it has sat for a time empty. The salts, calcium, rust, ect, that floats around in cooling systems dry and flake away when radiators sit unused for a while, and become a blocking problem when used again. If this is the way you are going to go, then try a radiator filter. Basically like a fabric sock, (the foot of a ladies stocking can be used) put this in your radiator hose, with it clamped in place to catch anything loose in the coolant system. It needs to be checked regularly, depending on how bad it is.

Growing old is compulsary, growing up isnt, and
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