I believe his oint is that it seems surprising to him that the engine worked fine after sitting for 4 years and having a lot of sand in the gas tank. Realistically though I don't see how the sand could do much damage. It has to get through at least two filters before it can junk up the carb or injectors.
I once ran a 289 with 200,000 miles on it for a few hundred miles with maybe
1/2 gallon of coolant. Broke the temp sender so I never knew it was overheating. I had just put on a pair of open chamber 302 heads and I fully expected it to be a gutless wonder with those big open chamber heads and only 100 PSI of compression (surprisingly within a couple PSI on all cylinders). Anyhow, I ran it several hundred miles before I realized I forgot to refill the coolant system. Not easdy miles either, running WOT on the highway for hours at a time, doing about 80, more downhill.That sucker musta been overheated out the wazoo, but it kept on running until finally on the highway I thought back and couldn't remember ever filling the radiator. OOPS! So I pulled over, what water I had with me in the radiator, then went and got water. After filling the coolant system the car ran much better. It had a top speed of around 100, maybe a little more. So I could then cruise at my 75-80 MPH without flooring it. The engine seemed a good bit more 'peppy' in general, though it was still a gutless wonder (especially in a nearly 2 ton car). That was my first car though, so I did some stupid stuff along the way to learning about cars. Like that time I ran for a week with only a quart of oil (oil light came on when braking or turning hard).
Built Ford tough I say. it definitely took some punishment. After all that, and hearing other people call the 289 the forever engine (one guy said he had one go to well over 300,000 miles), I believe Fords 289 is one of the most reliable and durable engines ever built. It's a very simple engine with a great design. It's a nice short stroke, and a rather 'square' engine which reduces wear and stress and also lets them rev nicely. It's just a solid design, and easy to work on too.
Cory