400Smallblock83

I know this isn't about an LSx Motor but need help. I'm having a little trouble with my 91 Z28. I had the engine extensivly modifyed by a local performance shop. Because of a too busy work schedule I had the speed shop do the installation as well as the engine build-up. Everything was great for about 12,000 miles, then the engine started to run very rough. It was burning coolant. I removed the engine, replaced the head gaskets and a damaged oil pan. I reinstalled the engine and now there is no spark. There is no spark at the plugs so I replaced the distributer module. Nothing. I pulled the coil wire and there is no arcing when I crank the engine. My question is, how do I trouble shoot this ignition problem?

Thanks!