More than a PDF file thread we need a "cross-referenced parts" page to show what parts from other vehicles can be used, and also a "cheaper alternatives" thread
There was also a thread that had all the parts manuals. You can kind of cross reference with that by just searching the Dodge part number, though it doesn't always tell the full story. I know Roe Racing has all the parts diagrams on their site as well.
The "cheaper alternatives" is the tricky part. One good example is the lifters in the engine. The Viper ones are quite expensive and only really cross reference to the Viper, but by all measurements and use tables the LA series Magnum engines appear to be the same thing and will fit. I think the bigger issue there probably has to do with quality and precision. They might all be "the same" from an engineering technical drawing standpoint (as in they all have common dimensions), but the different part numbers could denote different approved vendors that can meet the necessary quality requirements for the different engines or maybe they have different heat treatments or surface finishes or something like that. You can roll the dice and try whatever you want though. If you are going aftermarket then it might be less issue anyway. Crower for instance makes an aftermarket lifter for the Viper. The main difference in their part numbers just has to do with how many come in a kit (ie. enough for 8 cylinders vs enough for 10). The base part number is the same, just a quantity difference.