The main components of value include the block, the crank, the mains, and the valve covers, timing chain cover and oil pan. The water pump, distributor, intake, etc. are generally not used on a subsequent 409 performance build. The 333 heads are options that can be built out with better hardware valves, keepers, etc.).
Low mileage truck engines can sometimes be had for less than the cost of the block, the disclaimer being that upon disassembly some damage can be discovered. I got lucky on a 21,000 mile C60 409 truck engine.
Good luck!
TomK