The 20W-20 would be perfect for any application calling for a thirty grade as would the SAE 30.
Five hundred bucks for fifty five gallons of oil would be pretty reasonable.
From what I could see, this looks like API SE, so a fairly obsolete spec that worked when we used it back in the seventies and early eighties.
These would not be long drain oils but for the dollars the days of 3K drains could be brought back to life.
OTOH, there have recently been better deals on more modern and arguably better oils, like the clearance Havoline from O'Reilly's or the clearance Rotella T5 from AZ.