Sounds like some machine shop magic, Not Good. I would thing that undersized bearing are still available for that engine. Glad you were able to discuss this with the PO, answered a few of your questions about low oil pressure. I think your going to be fine once you correct the bearing issue.

~ Craig
1958 Viking 4400
"The Book of Thor"
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1960 Chevrolet C10
"A Family Heirloom"
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'59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)

If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane