The Stovebolt Site Forums The Shop Area Engine Shop Engine too rusty?

To just add to what Jerry said above, I don't think you are going to find the block and other cast iron parts all that rusty actually. The internal coolant passages are going to be rough as that's how they were cast, so don't let that misguide you that the block, head and other cast iron parts are going to simply fail from rust. Absolutely replace all the coolant passage block core plugs, but before you do, be sure to give those passages a thorough look and cleaning, especially behind that rear plug and the one on the driver side rear most plug opening as those area are known to collect/build up junk and debris which can seriously restrict and even block the coolant passages. Be sure to remove and clean out the drivers side block draincock/plug at the same time.

The other thing to inspect closely is the engine tins. Oil pan, timing gears cover, block side cover and valve cover are just thin sheet metal and can rust through if left alone for as long as your truck has sat.