OK, next question: I have decoded the VIN #, but am now trying to decode the engine casting. The # on the block, between the intake & the water pump is: 557752-3B. Any ideas? Thanks.

That should be a 77-80 350, with windowed main webs.

In terms of building an engine for power, the windowed mains are "undesirable" because the windowed blocks aren't as strong. On the other hand, they are lighter. For a semi-stock street cruiser, it will be just fine. There should be another machined pad on the block that has the VIN stamp in it- If the numbers on the pad match the VIN, it's the original engine.