Oil in my radiator

Pressure test it to 15psi, or more if you dare.
If it holds, flush the system, refill with water, drive it for a few hours. Let her cool, pop the cap blot the crud out, cap it and more run-time. Repeat as often as necessary to get the crud out.
But if the oil remains or gets worse, then you will have to do a cylinder air pressure test (about 80 psi) with the pistons at exactly TDC.
And if that fails to prove anything, then that test will have to be repeated, but with the pistons at BDC. To do this the rocker arm shafts will have to be removed, or the bolts at least completely backed off, so the valves are closed.Also,in this position you can crank the pressure to the moon! If you find a leaker, check the rad.........
After the problem is repaired, don't forget to dump the water out of the cooling system,before winter....