i just put a 4 core aluminum radiator in my 89 bronco *7.3idi swapped in* and have put about 60 miles on it fine tuning my swap and getting everything working. That said i have yet to get the temp up to kick on my fan. all light miles, as i said playing with things to get everything working. sits right around 170-180, think the fan kicks at 190?
Being that its a stock 460 rad, you might have cooling issues, but from what i can tell a 4 core aluminum (351W spec rad) is doing the job. Maybe try your local parts store and get a nice aluminum one and you should be good.