Engine timing mechanical

It can be off if the balancer ring has slipped, but I don't believe that's the case. 12* initial is way too low. That's why it's running hot. The mixture is still burning exiting the exhaust ports, because the ignition is firing too late and that's putting a lot of heat in the engine bay. Try jacking the initial up to around 18-20 and then limit total back down to 32-34. Big blocks generally like a little less total than small blocks. Whereas small blocks take around 36 give or take, big blocks like a little less. I believe it's the low initial timing that's your problem.

That said, I also agree with everyone that you need to verify TDC first.