Although it's fine to plug emblem and trim holes with body filler, it requires dimpling the hole to give the filler something to hold onto. That means if you ever wanted to replace your trim parts, you'd have to bang the dents out of every trim hole you filled. I think you'd be better off welding the holes with a mig and redrilling the holes later would be much easier than beating out 73 dents you intentionally put in to avoid welding. At least you'd still be able to see where the holes were located on the backside of the fenders when the time came. I totally understand the desire to not ruin a nice car, since I had to ask myself how badly I wanted a Shelby clone before I cut out an absolutely perfect taillight panel and then took a 3" hole saw to install my brake scoops. Yes, it hurt, but in the end I decided nothing is really irreversable and it is just a plain-Jane 2 barrel 289 car with no real collector value, and at least a high-quality Shelby clone would appeal to me. Like the saying goes, you can't make an omelet without breaking a few eggs...