I agree that if the truck is not in bad shape then don't restore it. I've worked on a couple of tonka trucks and they are not too hard to restore and fun. Biggest thing is make sure you keep track of the little parts and the important parts because even though you can find them on ebay it always seems the one part you need is the expensive one (for example I had to pay 20 bucks for a grille for the truck I'm using for my steam tonka truck project)
Here's one that I'm working on right now. Not done yet but I did have to patch a hole in the roof that showed up after I removed the rust and I lost a headlight when I picked the darn thing up but it's not looking too bad so far (not a professional job but it should look nice when I'm done)
And here is what the truck looks like as of now (can't even tell where the hole in the roof next to the rear roof support was)