Not sure about 78-82, I think they have a divider in the center that matches the center bar of the grill. Single headlights thru 79 had round headlights I am thinking. I bought mine from Rockauto.com for my 85, check them, their source is usually Sherman Collision parts, you can Google them. If they don't have them, they may not be available new any more.
'85 GMC Shorty
'99 AWD Astro
'55 Chevy 150 ex-racer
"I thought you weren't allowed to talk to guys with vans??"