Will 4.3 Chevy engine start 180 degrees out on the timing?

No, a 4.3L Chevy engine (or any internal combustion engine for that matter) will almost certainly not start 180 degrees out of timing. Being 180 degrees off means the pistons are trying to compress when they should be expanding, and vice-versa. This creates a complete conflict of forces within the engine, preventing it from turning over or even possibly causing damage. The engine will likely just crank without firing.