Losing my mind trying to get this 360 to run right

Ok so here's some more info. The motor fires right up first rotation. It's not backfiring through the carb its popping through the exhaust and it could be the scavenging and hot headers. I can't really get a good timing gauge because it won't idle and when it gets the rpms low enough it dies. I reran the valves the other day to make sure all was good so I checked that off the list. I've made sure all vacuume leaks have been checked and so far everything seems good. Heads have been completely rebuilt with all new parts. I'm thinking I should get the exhaust back on because tuning is going to change vastly after the exhaust is on. I built the motor so I know everything that has been done to it. Float levels and fuel pressure is good. I scored a new carb this evening as a test mule to rule out the 750 that's on there. Thanks for all the suggestions guys ill do a compression test on it tomorrow just to be on the safe side. If I can get her to idle then I can really narrow down the timing and hopefully get this sucker somewhat running right. I'm thinking seriously I need to get the exhaust on. Ill post a video of it running tomorrow.