We don't want to go totally off the page, like "Forty Weight Non Detergent" or the like, but beyond that I think pretty much anything in the mainstream (and everything said so far is mainstream!) will be just fine. I used to be a fan on single-weight oils, ran 30HD in all our vehicles which at the time were all Detroit Iron. Because of being in FL, the single weight worked all year.
Nowadays, I'd say 10W30 for a 460/7.5L. We ran that in the 1983 460 we had and no issues. Had over 100,000 miles.
I actually started to repeat an observation I see often on the boating forum I also hang out on: "How many engine failures have you traced to Oil Failure, Wrong Oil?" The manufacturers love to intimidate owners into their products. If you think the auto/truck manufacturers are pushy, check the Outboard manufacturers and MerCruiser (which is a GM engine!). They make it think the earth has turned flat and you'll sail off the edge if their oil's not in your crankcase.
I've only heard of two oils going flaky.
1. The early 10w40. There was something about the viscosity additive that allowed at least some of that oil to fail and some car builders claimed they'd deny warranty if 10w40 continued to be used. Even though it had been listed in Owner's Manuals!
2. Quaker State awhile ago. A friend said he had a crankcase of it turn to a jelly. A neighbor said he tore an engine down and the inside looked like it was covered in cinders. I DID actually witness that in a V6 Buick engine. I had the intake manifold and oil pan off, and actually chipped/scraped crusty deposits (not sludge) out of it.
In those days (late 1980's/early 1990's) you could see a black trace in the bottom of a bottle of oil based on "Pennsylvania Crude." Still I believe both of those oil issues above are history.
GOOD Oil, GOOD Filter, Changed Frequently the first couple times...
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB