I built this kit as an MPC labeled kit about 35 years ago, and don't recall having too many problems with it, so it must be a decent kit as I was 16 or 17 at the time. I did just buy another MPC version last year as I no longer have the model I built as a youth, but don't plan on building it for another year or two. I don't really pay too much attention to any minor inaccuracies that occur in some kits, so to me this one is just fine visually. I do agree on the tires being a tad bit off size wise, and maybe the wheels too, but overall it should build into a pretty snazzy model kit replica. 3D Model Specialties by Ron Olsen on Shapeways does have some 1/16 scale parts available, but I'm not sure if any would be usable on the Cobra kit, I guess it would depend on personal preference. Might even be other 1/16 scale parts suppliers on Shapeways too. Anyways, this is the box art for the kit I did way back when and just purchased another of last year...
Also here are a couple of links to youtube vids.