Hello gerahead,
Chances are the PO kept adding to fill low spots instead of sanding to level with original metal. I've seen that happen a lot on prior resto's that my Dad and I performed (Old Bentley's Rolls, Jags, etc...) When we were finished working metal back into shape, we ended up with an absolute minimum of filler, in many cases skim coating and a light bolck was enought to quell previous issues. Long blocks such as those developed by AFS and durablock go a long way to truly flattening filler and primer. Our vehicles have some pretty long and flat surfaces and the longer the block the better. Sometimes in a pinch you can use some metal to metal by evercoat to initiate restructuring of body lines and due to its inclusion of aluminum into the resin and polymer, the repair will shape and hold as nice as led. I am a firm believer in re-leding where the factory originally performed led work. Nothing lasts longer! Keep up the good work. A great paint job isn't necessarily about the paint itself. It's all in the detail and prep.