Well, it is a tough choice.This site recently had a contributor with a problem similar to yours. Most here thought he should just oil it as you suggest, but he also was likely to have it judged on originality, so he felt the need to paint it where it was orginally like that. We all love the look of beautiful wood.That's why most restord AD trucks have beautiful wood beds which of course they were never built with. So I would consider what you plan to do with your '28.Check with AACA for ideas too.
