These are Dodge flares, but I have heard they can be made to work on Chevy's. KC confirmed that this can be done. I think Bvrwally has them on this van too???
https://vintage-vans.forumotion.com/a-van-general-discussion-f3/fender-flares-t2952.htm
https://vintage-vans.forumotion.com/a-van-general-discussion-f3/fender-flares-t2952.htm