you can use 5w30...it is just a little thicker than 5w20 when up to temperature. same flow at low temps, thicker at high.
Valvoline's MaxLife does come in a 5w20, you might have to see if your parts store will order some in special for you. My '98 is backspec'd to 5w20...but since I'm on track for only 7k miles per year...it is going to take me a while till my next change.
Advance Auto Parts: MaxLife 5W-20 Synthetic Blend Motor Oil (1 qt.) by MaxLife - Part VV169
I know my Advance does not have that readily on the shelves...but I'm sure they could get my order in within a few days.
Oh, and Castrol makes a 5w20 high mileage oil as well.
Mine: '98 Ranger XLT 3.0L SuperCab w/ manual 4x4 "Off Road" 193k miles
Wife: '07 Mitsubishi Outlander LS AWD 3.0L 128k miles
My 3.0 puts out 150HP...hers puts 220HP...something is wrong here!
Future Restoration: '77 Chevy 2WD K5 Blazer