[Fordhcw]

You should get a used oil pan from a junk yard or take the old one to a welding shop or radiator repair shop. Epoxy is only good for a temporary fix at such high temperatures. Part of the problem is that the thermal expansion and contraction of the steel epoxy joint occurs two or more times daily. Plastics tend to harden and become brittle as they age. The hot oil may weaken the epoxy's bonding strength and the patch could fall off without warning.
I once put fiberglass cloth and epoxy around a rusty gas tank, but the gasoline softened the epoxy and the tank began to leak. Epoxy does not bond very well to steel even if the surface is sanded. Over time the hot oil may weaken the epoxy in the same way that gasoline does.