That may or may not be true. It depends on how long you want to keep the truck and how good you are at finding good used engines. The big expense is involved with rebuilding a 7.3 "right" which means dry sleeves which means a good machinist= BIG $$. It also depends on if you know somebody to do that work cheap for you and what if anything can be salvaged out of the old engine. Sleeves are usually around $100 and up per cylinder. You can bore a 7.3 but you may be on cavitation's doorstep...maybe not either if you know the history of the engine and know it hasn't failed from this before and has had the SCAs maintained all of its life. Rebuild kits exist but they aren't very cheap. I think Northern Autoparts ? has them for around 500-1000 bucks rings, pistons, and gaskets, maybe bearings too. Anything else would be more $$. A drop in reman engine or a custom build up would be best but most money a used running engine might be cheapest but most risky. A used 6.9 is probably OK if you change the headgaskets and it starts easy with not too much blowby. A used 7.3 may be on cavitation's doorstep or have a bad valve like you think this engine did and have little to no obvious symptoms. Oil cooler and head gaskets are too easy not to do when the engine is out of the truck.