1977 Dodge Sportsman 440cu oil capacity?

I just got a 1977 Dodge 27ft motorhome with a 440cu engine w/45,000mi. I have searched the web for oil capacity and found from 6qts w/filter to 9qts. Today I changed the oil and filter and put in 5qts to start up and check dip stick oil level. Well at 5qts it had no oil pressure, would not pick up the oil. I added 1 more qt and oil pressure went to 65psi, good. I think my oil dip stick is not the right one. This means at 1 qt low I would have no oil pressure. That want work. How much oil does some of your old Dodge MH take?
With 6qts my dip stick say a little over full.

Thanks Harold in Florida.