One of the issues is the factory rods. When you have to hone them out of round, there's a lot for want there.....
Now we have modern rods and modern
oil pans, and the issues are not really issues anymore.
Even the 427's were not immune to issues and there aren't many out there that are raced "as stock", and as a matter of fact, there are oiling modifications that have to be done to brand spankin' new aftermarket blocks from BBM, Pond, Shelby, etc.
Unless someone is craving the magic "427" number, there's literally zero reasons you should have to bypass a 390 to build an engine. I can make 100 hp more with a 390 than any 427 made from the mid 60's. You can literally have a 390 block that has been prepped/machined sitting in your lap for $1000 and with the right parts make well over 500 hp.